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C o nt e n t s
Preface xi
1. Introduction 3
Getting Connected 5
Networks as Information Maps 6
Leaders and Followers 8
Networks as Conduits 8
The Point of View 10
2. Basic Network Concepts, Part I: Individual Members of Networks 13
Introduction 13
What Is a Network? 14
Sociological Questions about Relationships 17
Connections 17
Propinquity 18
Homophily 18
Individual-Level Homophily 19
Homophily and Collectivities 20
Dyads and Mutuality 21
Balance and Triads 22
Where We Are Now 26
3. Basic Network Concepts, Part II: Whole Social Networks 27
Distributions 29
Dyads and Triads 29
Density 29
Structural Holes 29
Weak Ties 30
8.
m m
viii jContents
"Popularity" or Centrality 31
Distance 32
Size of the Interpersonal Environment 34
The "Small World" 35
Multiplexity 35
Roles and Positions 38
Named Positions and Relationships 38 <,
Informal Positions and Relationships 39
Informal Relations and Hierarchies 39
Embeddedness of the Informal within Instituted or Named Networks 40
Observed Roles 41
Summary 42
4. Basic Network Concepts, Part III: Network Segmentation 44
Introduction 44
Named and Unnamed Network Segments 45
Primary Groups, Cliques, and Clusters 46
Segmenting Networks from the Point of View of the Observer 46
Segmenting Groups on the Basis of Cohesion 47
Resistance to Disruption 48
Structural Similarity and Structural Equivalence 49
Core/Periphery Structures 50
Where We Are Now 55
5. The Psychological Foundations of Social Networks 56
Getting Things Done 57
Community and Support 58
Safety and Affiliation 59
Effectiveness and Structural Holes 59
Safety and Social Networks 60
Effectiveness and Social Networks 62
Both Safety and Effectiveness? 63
Driving for Status or Rank 65
Cultural Differences in Safety, Effectance, and Rank 66
Motivations and Practical Networks 66
Motivations of Corporate Actors 68
Cognitive Limits on Individual Networks 70
Where We Are Now 72
6. Small Groups, Leadership, and Social Networks: The Basic Building Blocks 74
Introduction 74
Primary Groups and Informal Systems: Propositions 75
Contents I ix
Pure Informal Systems 77
How to Find Informal Systems 78
Asymmetric Ties and the Influence of the External System 82
Formalizing the System 85
Where We Are Now 88
7. Organizations and Networks 90
The Contradictions of Authority 91
Emergent Networks in Organizations 92
The Factory Floor 92
Information-Driven Organizations 94
Inside the Box, Outside the Box, or Both 100
Bridging the Gaps: Tradeoffs between Network Size, Diversity, and Social Cohesion 103
Where We Are Now 106
8. The Small World, Circles, and Communities 108
Introduction 108
How Many People Do You Know? 110
The Skewed Distribution of the Number of People One Knows 113
Formal Small World Models 119
Clustering in Social Networks 122
Social Circles 123
The Small World Search 128
Applications of Small World Theory to Smaller Worlds 130
Where We Are Now 132
9. Networks, Influence, and Diffusion 135
Networks and Diffusion—An Introduction 135
The Basic Model 137
Exogenous Factors in the Adoption of Innovations 139
Influence and Decision-Making 139
The Current State of Personal Influence 141
Self-Designated Opinion Leaders or Influentials 143
Characteristics of Opinion Leaders and Influentials 145
Group Influence 146
Epidemiology and Network Diffusion 148
Social Networks and Epidemiology 148
Social Networks and HIV-AIDS 150
Transporting Disease—Large-Scale Models 152
Tipping Points and Thresholds 153
Threshold 155
Where We Are Now 159
9.
x I Contents
10.Networks as Social Capital 162
Introduction 162
The General Idea of Social Capital 164
Social Capital as an Investment 165
Individual-Level Social Capital 168
Social Support 168
Individual Networked Resources: Position and Resource Generators 170
Correlates of Individual Social Capital 172 i*
Other Indicators of Networked Resources 173
Social Capital as an Attribute of Social Systems 175
Theorists of Social System Social Capital 175
BowlingAlone 177
Recent Findings on Social System Social Capital and Its Consequences 178
Where We Are Now 181
11. Ethical Dilemmas of Social Network Research 185
Networks as a Research Paradigm 185
Anonymity, Confidentiality, Privacy, and Consent 187
Who Benefits 189
Cases and Examples 191
Survey Research 191
Organization Research 194
Terrorists and Criminals 195
Networks and Terrorism: The CASOS Projects 196
Conclusion: More Complicated than the Belmont Report 198
12. Coda: Ten Master Ideas of Social Networks 201
Introduction 201
The Ten Master Ideas 202
NOTES 213
BIBLIOGRAPHY 223
INDEX 247
P r e f a c e
WHEN I WAS a graduate student, before the term "social networks" came into general
use, Paul F. Lazersfeld introduced his students to the idea of personal influence as a
major factor in decision-making. Robert K. Merton had his seminar students read
Georg Simmel line by line, among other matters explicating the ideas of triads and
social circles. These teachings formed my introduction to social networks as problem-
solving tools in understanding why people went to psychiatrists and how elites were
organized. Hans Zetterberg insisted that socialtheory could and shouldbe systematic.
I am grateful to these mentors for getting me started on what became the study of
social networks as key methodological and theoretical insights that could help to
unpack social phenomena. I remain as much interested in the impact of social net-
works on social"structure and cultural content as I am in the study of networks them-
selves. This book reflects that bias.
The Cohen Center for Modern Jewish Studies at Brandeis University, my colleagues
there, and especially the director, Leonard Saxe, were extremely supportive while I was
writing this book making time and intellectual space for the effort. Deborah Grant,
managing editor of the Center, turned the manuscript into readable prose. Katherine
Ulrich was a meticulous copy editor. I am grateful to the Brandeis Libraries for their
wide subscriptions to electronic journals and databases, making it easier to download
an article than to go to my own library and find the hard copy version. Peter Prescott
provided sage advice about publishing.
The socialnetwork field is sobroadthat it is almost impossible for a single individual
to encompass it and get everything right and make things understandable to the non-
mathematically inclined. To the extent that I managed at all is because a number of
people have helped and encouraged me. Foremost is James Moody who reviewed an
XI
10.
xii I Preface
earlierversion of the manuscript and gently pointed out omissions and commissions,
and gave me feedback from a class to which he assigned that earlier version. Thomas
Valente introduced me to Oxford University Press, provided me with an early draft of
his very useful book Social networks and health: Models, methods, and applications, and
was helpful in many other ways. Claude Fischer reviewed the chapters on concepts and
several others as well. Others reviewed one or more chapters and are acknowledged in
a footnote at the beginning of each chapter. They include: Richard Alba, H. Russell
Bernard, the late S. D. Berkowitz, Andrew Braun, Michael Brimm, Cynthia F. Epstein,
Linton Freeman, Bethamie Horowitz, Dani Maman, Amalya Oliver, Stuart Pizer,
Robert Putnam, Gary Robins, Theodore Sasson, Leonard Saxe, Tom Snijders, Barry
Wellman, and Douglas R. White. Remaining errors and infelicities are of course my
responsibility.
My wife, Ghislaine Boulanger, who knows well the pangs of authorship, supported
me throughout.
Fishers Island, July, 2011.
UNDERSTANDING SOCIAL NETWORKS
11.
F
it
Introduction
"NETWORKING" SEEMS TObe on everyone lips. No one simplygoes to aparty anymore.
They go to network. For many people, the World Wide Web exists for the main purpose
of making connections. Networking seems familiar yet mysterious, accessible yet
arcane. Social networks, however, have been at the core of human society since we were
hunters and gatherers. People were tied together through their relations with one an-
other and their dependence on one another. Tribes, totems, and hierarchies may have
come later. Kinship and family relations are social networks. Neighborhoods, villages,
and cities are crisscrossed with networks of obligations and relationships. Beyond kin-
ship relations, people in modern societies are dependent upon one another for such
things as picking up the mail when one is away, help withfixingthe lawn mower, or rec-
ommendations for good restaurants. Nonetheless, it is said that urban Americans are
becoming more and more socially isolated. The metaphor of "bowling alone," rather
than in clubs, leagues, or with friends; describes this picture of isolation and disengage-
ment (Putnam 2000). But rather than disappearing*, neighborhood and village-based
groups celebrated as the heart "ofnineteenth-centuryAmericahave become transformed
from social relations and networks based on place or kinship into communities oriented
around geographically dispersed social networks.1
The telephone and automobile
started this revolution and were, not surprisingly, popular in rural areas where there
were great*distances between households. We have been "networkers" for millennia.
Networks <are not the same thing as "networking," or actively using a network to
make connections to further one's personal goals. A network is simply a set of rela-
tions between objects which could be people, organizations, nations, items found in a
12.
4 | UnderstandingSocial Networks
Google search, brain cells, or electrical transformers. Transformers do not "network."
In this book we are concerned with social networks, and what passes through these
networks—friendship, love, money, power, ideas, and even disease.
Has the internet, itself an example of a huge network, changed the rules of social
networks? Less than has been claimed. Though people's networks contain substantial
numbers of friends, neighbors, relatives, and workmates who are locally based, social
networks are supplemented by new internet-based media. It is not a matter of one
replacing the other; rather, the "internet fits seamlessly with in-person and phone en-
counters .. .The more that people see each other in person and talKfpn the phone, the
more they use the internet" (Boase et al. 2006). Social networks areresilient and con-
stantly adapting. Large "mass societies" remain bound by personal ties.
So while the mass media may have "discovered" social networks—a few years ago
the New York Times celebrated social networks as one the "new ideas" of 2003 (Gertner
2003)—what is relatively new are systematic ways of talking about social networks,
depicting them, analyzing them, and showing how they are related to more formal
social arrangements such as organizations and governments. In 2008 alone, Science
Citations Index found 1,269 articles on "social network" or "social networks." In the last
10 years, the total figure is 6,304. The growth is linear. Since 1984, there has also been
rapid growth in the number of substantive areas to which social network analysis has
been applied, from train schedules in China to the HIV epidemic. The popular press
and blogs have been deluged with writing about social networks. Recently, Google
listed over 52 million entries for "social networks."
Nonetheless, there is something mysterious about social networks. We live sur-
rounded by them, but usually cannot see more than one step beyond the people we are
directly connected to, if that. It is like being stuck in a traffic jam surrounded by cars
and trucks. The traffic helicopter can see beyond our immediate surroundings and sug-
gest routes that might extricate us. Network analysis is like that helicopter. It allows us
to see beyond our immediate circle.
This book aims to take away some of the mystery about social networks by explaining
the big ideas that underlie the social network phenomenon. I concentrate on the concepts,
theories, and findings of the social network field. Intended for readers with no or a very
limited background in mathematics or computers, this is not a "how to do it" book. There
are manyuseful hooks that help the reader, often assuming the aid of an instructor, to ana-
lyze, deconstruct, and display social networks with the aid of computers. Here I attempt
rather to explain the concepts, theories, and findings developed by network experts. Be-
cause I am a sociologist, the book has a structural social science bias, but it also takes
account ofpeople and their motives. I hope itwillbe useful to social scientists whq encoun-
ter social network research in their readingandwish to knowmore aboutit and to students
new to the network field. I also hope it will be useful to managers, marketers, and ol^iers
who constantly encounter social networks in their work life. Maybe avicLsodal "network-
ers" will find it useful. Graphics-are important to the network field. So, when thereis a
mathematical basis for network ideas and findings, I try to present them as a graph-.
There is a lot to cover, and if the rapidgrowth of thefieldis anyguide, the comingyears
will see even more work. There are two contrary trends in anyfield:investigators build on
Introduction l 5
the basic work of others and stand on the shoulders of giants (Merton 1993), but at the
same time they strive to make previous work obsolete. While recognizing that the social
networkfieldis moving swiftly, I attempt to select material that serves as basic building
blocks and examples of best practices that will allow the reader to understand and eval-
uate new developments as they emerge. By the time the reader has finished the book,
there maywell be important new discoveries in understanding social networks and their
myriads of applications. Social network sites are burgeoning systems that in the hands
of ordinary people as well as revolutionaries may—or may not—be changing the course
of history. Yet sound research on these sites-is still in its infancy. My hope is that this
book will give you the concepts and ideas to understand research and accounts of devel-
opments in social networks that are now almost unimaginable.
A few examples that dramatically capture the current state of the art of the field are
the best way to begin to understand what social networks and social network research
is all about: getting connected; networks as information maps; leaders and followers;
and networks as conduits.
Getting Connected
Everyone could be connected, if only we knew how to reach out beyond our immediate
horizons. One of the signs of the growth of the social network field is the very idea of
"networking,"2
especially with the aid of the internet. Making connections through
social network sites and the internet is ever increasing. It is not confined to adoles-
cents looking for more friends. As of December 2008,75% of the U.S. adult population
used the internet. Of these, 35% now have a profile on an online social network site, up
more than fourfold from 8% in 2005.3
Seventy-five percent of adults 18 through 24
have a profile and almost 70% of students and teenagers, suggesting that as these co-
horts age, the total proportion of the U.S. population using social network sites can
only rise.4
Almost 90% of adults use their online profiles to keep up with friends, and
half use it to make new friends. Internet-based social networking is more common
among urban dwellers who perhaps might feel otherwise more isolated. Facebook,
founded in 2004 as a social networking service for Harvard students, is currently
(2010) valued at $50 billion dollars. According to the research firm ComScore's 2009
Digital Year in Review, it has surpassed MySpace and attracted 112 million visitors in
December 2009, up over 100% during the year. As of July 2010, Facebook claimed 500
million active users worldwide. Twitter, publicly released in August 2006, is a social
networking service that enables anyone to post messages of no more than 140 charac-
ters, known as tweets, to people who sign up as self-designated followers. ComScore
reported 20 million visitors for Twitter in December 2009, up tenfold from the previ-
ous year. Google, the leading search engine that aids social networking services, is also
based on network ideas first developed for citation analysis in the 1950s. All these sites
and services are free to the user.5
Social network sites have profound implications. Suppose the number of "friends"
you have on your profile is a modest 100. If none of them is a friend of the other, then
13.
6 | UnderstandingSocial Networks
two steps removed, you have access to 10,000 people (100 times 100), who can also
reach you. Three steps removed there are 1,000,000 (100 times 100 times 100). Soon,
the entire world is a potential friend, for better or for worse. No wonder you hear from
people who want to be your friend, many of whom you have never before heard from.
There is some danger in this, for you may be exposed to more people than you may
have desired. The world is indeed "small."'The implications for network theory will be
expanded upon later in the book in a chapter on the "Small World."
As "social networkers" hope, these connections can be useful. Connections have the
potential to give a person access to valuable resources such as: referral to jobs by people
out of one's immediate circle who might know of jobs one's close friends are unaware of
(Granovetter 1973); ability to rise in the social ladder of occupations (Lin and Erickson
2008a); help with personal problems (Thoits 1995); referral to a good restaurant, book, or
movie (Erickson 1996); or someone who can pick up your mail when you are away (Fis-
cher 1982). These networked resources that you do not own, but to which you have access
through your friends and acquaintances, are called "social capital" (Mouw 2006).
Networks as Information Maps
Social network analysis reveals what is hidden in plain sight. When you buy a book from
Amazon, the site tells you what other books those who bought your selection also
bought. I myself have succumbed to this marketing application of networks and bought
books I might not have otherwise considered. Using network analysis principles, Valdis
Krebs, an organization consultant who specializes in social network applications, ex-
ploited the Amazon data to create on his blog6
a map of books related to the 2008 presi-
dential campaign. Below is his map of books bought by the same people (figure 1.1). The
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Introduction I 7
arrows show, for example, that people who bought Dreams from My Father also bought
Change We Can Believe In.
There is an Obama cluster of books in the upper left corner; a Democratic campaign
cluster in the middle, and a Republican group on the right. There is no overlap between
the clusters. In 2008, the reading population of America was polarized, a significant
augur for subsequent political polarization. Rules for Radicals, by radical community
organizer Saul Alinsky, does not fit the partisan tone of the rest of the books in the
Republican cluster and was bought by people who bought anti-Democrat and anti-
Obama books. One supposes that they wanted to learn about some of the successful
grassroots organizing principles of the Left. "Tea Party" organizers?
Network ideas are useful for displaying data such as who bought what book but are
especially helpful in making sense of news that involves connections, such as who was
involved in what banking deal, who was tied to Madoff's Ponzi scheme, or who was in
the network of 9/11 highjackers. Newspapers and Web news sites increasingly use
them. Displays of networks on the Web are especially useful because they can be inter-
active, allowing further information about the points in the network. We can not do
this in a book, but figure 1.2, provides an example from Slate of the network implied in
the Mitchell Report7
that connected baseball trainers and players involved in providing
FIGURE 1.1 Books Bought by the Same People in the 2008 Presidential Campaign with the kind
permission ofValdis Krebs
PIGURE 1.2 Detail from a Network Depicting Connections in Performance-Enhancing Drug
Usage in Baseball.
With the kind permission ofWashingtonpost.newsweek Interactive (WPNI), publisher ofSlate Magazine
Slate: The steroids social network. An interactive feature on the Mitchell report. By Adam Perer and Chris
Wilson Updated Friday, December 21, 2007, at 11:12 A
M ET. The figure is produced by Social Action software
developed byThe Human-Computer Interaction Lab ofthe University of Maryland.
12 i UnderstandingSocialNetworks
can they best be utilized? From time to time, we will reference classic social theorists
to see to what extent social network ideas illuminate the problems that they posed. In
this view, social networks are not only structural abstractions and the study of net-
works is not an alternative to classic ways of understanding society, but is a way of
gaining greater insight into social life. Though networks also characterize the inani-
mate world such as electrical power grids, social networks have to*!qe understood, to
quote E. F. Schumacher (1973), "as if people mattered." */
'' 1
Basic Network Concepts, Part I
INDIVIDUAL MEMBERS OF NETWORKS
Introduction
Social network theory is one of the few theories in social science that can be applied to
a variety of levels of analysis from small groups to entire global systems. The same
powerful concepts work with small groups, with organizations, nations, and interna-
tional systems.
Chapters 2-4 introduce elementary network concepts, the "score-card" without
which you cannot distinguish the players. In addition to defining the concepts, the
(.chapters provide some flavor of how they are used and how they are linked to basic
g.ideas about networks. This chapter introduces concepts concerning relations between
'the units that comprise a network. Chapter 3 discusses concepts that describe a net-
work as a whole. Chapter 4 addresses where to draw the line—partitioning whole net-
works. We begin with a definition of a simple network that connects pairs or dyads. We
^Conclude the chapter with a discussion of triads, the most elementary network in
Which the structure of the network really matters. For networks, dyads and triads are
f the analogue of molecules. Dyads and triads will give us a handle for understanding
[larger networks.
With dyads or pairs we are interested in why people come together—why they form
|a dyad in thefirstplace."As with all network theory, we will see that a feedback loop is
ttt the heart of network processes. There are forces such as propinquity—for example
|«eing in the same place at the same time—that bring people together; but at the same
jjtime, the dyad creates consequences for its members and for the whole network. People
1*3
17.
14 ! UnderstandingSocial Networks
who are connected with one another tend to be physically proximate. People who are
near to one another also tend to share the same characteristics, values, and social
statuses. This relationship is one of the reasons, for example, that desegregating neigh-
borhoods or integrating schools can be particularly challenging. Regardless of how the
connection happens, once people are linked, there is a tendency for them to acquire
the same characteristics, values, or social statuses from one another" Chicken-and-egg
problems abound in social network analyses. •''
The discussion above concerns "people," but the concepts apply tro all levels of net-
works including groups, organizations, and even nations. Some illustrations and a few
elementary propositions will be offered for each concept. Further applications of the
concepts, as well as more complex concepts and propositions, will be developed in later
chapters devoted to specific topics. While all the concepts have formalized means of
measurement, and often several different ways to measure the same concept, the aim
of this book is to develop the concept itself and show how it is applied in theoretical
statements and in substantive findings. Measurement issues will be noted and
referenced, but the mechanics of the analysis is mainly reserved for other literature.1
What Is a Network?
We begin with a more precise definition of "network": a network is a set of relation-
ships. More formally, a network contains a set of objects (in mathematical terms,
nodes) and a mapping or description of relations between the objects or nodes. The
simplest network contains two objects, 1 and 2, and one relationship that links them.
Nodes 1 and 2, for example, might be people, and the relationship that' links them
might be as simple as standing in the same room. If 1 is in the same room as 2, then 2
is in the same room as 1.2
The relationship is in figure 2.1a is not directional.
FIGURE 2.IA Simple Relationship
There are also directional relationships (figure a.i.b) such as 1 likes 2.
(b)
FIGURE 2.IB Directed Relationship
In this simple network of "liking," the relationship could be
Bask Network Concepts, Part I j 15
Nodes 1 and 2 like one another, or their liking is mutual. The liking network below
(figure 2.1c) is similar to the first one of standing in the same room together, but has
a valence or a flow. Mutuality is a tricky matter, however, and not all that easy to
achieve, so mutual networks tend to be limited. A prevalent tie between dyads is anti-
symmetric. Father and son, boss and employee are examples. The relationship is by
definition different, depending on which way you look.
(c)
• • i
FIGURE 2.1C Symmetric Relationship
There need not be just one relationship mapped between nodes 1 and 2. For exam-
ple, 1 and 2 might be in the same room and might also like one another. When there is
more than one relationship, this is called a multiplex relationship.
Aside from their directionality, or lack of it, relationships might be more than the
sharing of an attribute or being in the same place at the same time,.There can be a flow
between the objects or the nodes. Liking, for example, might lead to an exchange of
gifts. Flows and exchanges are very important in network theory.
At one level, this list of concepts of relationships between pairs of nodes is now logi-
cally complete. But consider a network (figure 2.id) between pairs that operates via an
intermediary node. For example:
symmetrical.
FIGURE 2. ID Relationship Through an Intermediary
Node 1 is connected to 3 via 2. The relationships shown above are directional and
not reciprocal. They might be transitive or they might not* be. If the relationship is
transitive, it means that if 1 loves 2, then 2 also loves 3. Possible, but not likely. Tran-
sitive relationships are more common in an official hierarchy. Node 1 gives a message
to 2 who forwards it to 3.
One can describe the network distance between pairs of nodes in terms of the
number of steps or links between them. There are obviously two steps between 1 and
3- But if 1 also likes 3, as shown below (figure 2.ie), the network is said to be transitive
or balanced and mutual and, in this case, all three nodes are directly linked.
The network depicted in figure 2.ie is a "sociogram"—a term invented by Jacob
Moreno (Moreno 1953 [1934]), who is regarded by many as a key founder of modern
network studies. It is also what mathematicians call a graph. There is a branch of
18.
16 j UnderstandingSocial Networks
FIGURE 2.IE Sociogram ofThree Nodes, All Mutually Related
mathematics, graph theory, which allows sociograms to be manipulated mathemati-
cally (Harary, Norman, and Cartwright 1965). The depiction of relationships as so-
ciograms allowed observers almost instant insight as to what was going on in small,
not overly complicated networks. The addition of graph theory to the tools for un-
derstanding networks further allowed for understanding and manipulating much
larger and more complex networks. In this introduction to network theory, we will
dispense with the mathematics of graph theory but will rely on its insights and find-
ings. The simple network of three units is called a triad. This simple network turns
out to be the building block of more complex relations and will be discussed at the
end of this chapter.
Many network analysts, and much of the software for manipulating networks,
prefer to work algebraically with networks when they are depicted and expressed as
matrices. Below (table 2.1) is the same sociogram but in matrix form. In network
terms, we call this an adjacency matrix because it shows who is next to whom.
The numbers, i, 2, and 3 on the top line and the first column identify the same
nodes as in figure 2.2. The number 1 on the second line indicates a connection between
the nodes. Node 1 "chooses" nodes 2 and 3. Node 2 "chooses" nodes 1 and 3. Node 3
"chooses" nodes 1 and 2. The dashes indicate that in this graph or matrix, self-choice is
not at play, though in some networks self-choice can be an option. For example, <andi-
dates in an election can vote for themselves.
TABLE 2.1
The Adjacency Matrix that
Represents Figure 1
i _ 1 _ _ _ a _ 3 _
j 1 1 1
12 1 - 1
l3 1 1
J
' '
Basic Network Concepts, Part I jp
Sociological Questions about Relationships
Though all of our examples thus far have been social, in principle, we might as well
have been talking about electrical currents. There is a branch of network theory that
deals with such matters, though electrical circuits tend to be considerably simpler than
social networks. But consider. At each level of analysis—individual, organization, or
nation-state, for example—what are the conditions that make it more or less likely
that a path will exist between two nodes, that the nodes will have the same attributes,
that they will be reciprocally or mutually related to one another, and that triads will be
balanced? The answers lie in social theory. We now introduce some elementary
hypotheses about these conditions.
Social scientists have investigated three kinds of networks: ego-centric, socio-
centric, and open-system networks. Ego-centric networks are those networks that
are connected with a single node or individual, for example, my good friends or all
the companies that do business with Widgets, Inc. (the favorite name of organiza-
tions studied in business schools). However, a list is not necessarily a network. In
popular discourse, especially when social support is discussed, any list is called a
"network." It is a network in a basic sense because even if no one on the list is
connected with one another, each individual is at least all connected with the person
being supported. The support may include help with a job search, comfort during an
illness, or a loan of money or a lawn mower. A person with a large number of good
friends whom he or she can count on is commonly said to have a large "network."
This network cannot be discussed in social network terms, however, unless we know
whether and how these people are connected with one another.3
It is obviously one
thing to have a supportive network in which most people know one another and a
very different matter if the people are unknown to one another. Ego networks and
how they extend further to links beyond the starting point are discussed in the next
chapter on whole networks.
Socio-centric networks are networks in a "box." Connections between children in a
classroom or between executives or workers in an organization are closed system net-
works and the ones most often studied in terms of the fine points of network struc-
ture. These were' the ones with which Moreno began his studies. Open system
networks are networks in which the boundaries are not necessarily clear, for they are
not in a box—for example, the elite of the United States, connections between corpo-
rations, the chain of infiuencers of a particular decision, or the adopters of new prac-
tices. In some ways, these are the most interesting networks. Later chapters in this
book, one about the "Small World" and one about diffusion, explore these open sys-
tems in some detail.
o
CONNECTIOlJ-S
We now examine some of the social situations and forces that make for connections
between one node (e.g., a person, an organization, a country) to another.
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eBook.
Title: Poisons, Their Effects and Detection
Author: Alexander Wynter Blyth
Release date: May 13, 2013 [eBook #42709]
Most recently updated: October 23, 2024
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*** START OF THE PROJECT GUTENBERG EBOOK POISONS, THEIR
EFFECTS AND DETECTION ***
POISONS:
THEIR EFFECTS ANDDETECTION.
BY THE SAME AUTHOR.
Fourth Edition. At Press.
FOODS:
THEIR COMPOSITION AND ANALYSIS.
With numerous Tables and Illustrations.
General Contents.
History of Adulteration—Legislation, Past and Present—Apparatus
useful to the Food Analyst—“Ash”—Sugar—Confectionery—Honey—
Treacle—Jams and Preserved Fruits—Starches—Wheaten-Flour—
Bread—Oats—Barley—Rye—Rice—Maize—Millet—Potato—Peas—
Chinese Peas—Lentils—Beans—Milk—Cream—Butter—Cheese—Tea—
Coffee—Cocoa and Chocolate—Alcohol—Brandy—Rum—Whisky—Gin
—Arrack—Liqueurs—Beer—Wine—Vinegar—Lemon and Lime Juice—
Mustard—Pepper—Sweet and Bitter Almond—Annatto—Olive Oil—
Water. Appendix: Text of English and American Adulteration Acts.
“Will be used by every Analyst.”—Lancet.
“Stands Unrivalled for completeness of information. . . . A really ‘practical’ work for
the guidance of practical men.”—Sanitary Record.
“An ADMIRABLE DIGEST of the most recent state of knowledge. . . . Interesting even to
lay-readers.”—Chemical News.
In Large 8vo, Handsome Cloth. 21s.
28.
FORENSIC MEDICINE
AND
TOXICOLOGY.
By J.DIXON MANN, M.D., F.R.C.P.,
Professor of Medical Jurisprudence and Toxicology in Owens College, Manchester;
Examiner in Forensic Medicine in the University of London, and in the Victoria
University; Physician to the Salford Royal Hospital.
Part I.—Forensic Medicine. Part II.—Insanity in its Medico-legal
Bearings. Part III.—Toxicology.
“By far the MOST RELIABLE, MOST SCIENTIFIC, and MOST MODERN book on Medical
Jurisprudence with which we are acquainted.”—Dublin Medical Journal.
“A most useful work of reference. . . . Of value to all those who, as medical men or
lawyers, are engaged in cases where the testimony of medical experts forms a
part of the evidence.”—The Law Journal.
London: Charles Griffin & Co., Ltd., Exeter St., Strand.
POISONS:
THEIR EFFECTS AND
DETECTION.
A MANUAL FOR THE USE OF
29.
ANALYTICAL
CHEMISTS AND EXPERTS.
WITHAN INTRODUCTORY ESSAY ON THE GROWTH OF MODERN
TOXICOLOGY.
BY
ALEXANDER WYNTER BLYTH,
M.R.C.S., F.I.C., F.C.S., &c.,
BARRISTER-AT-LAW; PUBLIC ANALYST FOR THE COUNTY OF
DEVON; AND MEDICAL OFFICER OF HEALTH AND PUBLIC ANALYST
FOR ST. MARYLEBONE.
THIRD EDITION, REVISED AND ENLARGED.
With Tables and Illustrations.
LONDON:
CHARLES GRIFFIN AND COMPANY, LIMITED,
EXETER STREET, STRAND.
1895.
(All Rights Reserved.)
D. VAN NOSTRAND COMPANY,
NEW YORK.
31.
PREFACE TO THETHIRD EDITION.
The present edition, which appears on the same general plan as
before, will yet be found to have been in great part re-written,
enlarged, and corrected.
Analytical methods which experience has shown to be faulty have
been omitted, and replaced by newer and more accurate processes.
The intimate connection which recent research has shown to exist
between the arrangement of the constituent parts of an organic
molecule and physiological action, has been considered at some
length in a separate chapter.
The cadaveric alkaloids or ptomaines, bodies playing so great a part
in food-poisoning and in the manifestations of disease, are in this
edition treated of as fully as the limits of the book will allow.
The author, therefore, trusts that these various improvements,
modifications, and corrections will enable “Poisons” to maintain the
position which it has for so many years held in the esteem of
toxicologists and of the medical profession generally.
The Court House, St. Marylebone,
W.
June, 1895.
33.
CONTENTS.
PART I.—INTRODUCTORY.
I. THEOLD POISON-LORE.
Section Page
1. The History of the Poison-lehre—The Origin of
Arrow-Poison—Greek Myths, 1
2. Knowledge of the Egyptians relative to Poisons
—Distillation of Peach-Water, 2
3. Roman and Greek Knowledge of Poison—
Sanction of Suicide among the Ancients—The
Classification of Poisons adopted by
Dioscorides, 2-4
4. Poisoning among Eastern Nations—Slow
Poisons, 4, 5
5. Hebrew Knowledge of Poisons, 5
6. The part which Poison has played in History—
Statira—Locusta—Britannicus—The Rise of
Anatomy—The Death of Alexander the Great—
of Pope Alexander VI.—The Commission of
Murder given by Charles le Mauvais—Royal
Poisoners—Charles IX.—King John—A Female
Poisoner boiled alive, 5-9
7. The Seventeenth Century Italian Schools of
Criminal Poisoning—The Council of Ten—John
9-13
34.
of Ragubo—The ProfessionalPoisoner—J. B.
Porta’s Treatise on Natural Magic—Toffana and
the “Acquetta di Napoli”—Organic Arsenical
Compounds—St. Croix and Madame de
Brinvilliers—Extraordinary Precautions for the
Preservation from Poison of the Infant Son of
Henry VIII.,
II. GROWTH AND DEVELOPMENT OF THE
MODERN METHODS OF CHEMICALLY DETECTING
POISONS.
8. Phases through which the Art of Detecting
Poisons has passed, 13
9. Treatise of Barthélémy d’Anglais—Hon. Robert
Boyle—Nicolas l’Emery’s Cours de Chimie—
Mead’s Mechanical Theory of Poisons—Rise of
Modern Chemistry—Scheele’s Discoveries, 13, 14
10. History of Marsh’s Test, 14, 15
11. Orfila and his Traité de Toxicologie—Orfila’s
Method of Experiment, 15
12. The Discovery of the Alkaloids—Separation of
Narcotine, Morphine, Strychnine, Delphinine,
Coniine, Codeine, Atropine, Aconitine, and
Hyoscyamine, 15, 16
13. Bibliography of the Chief Works on Toxicology
of the Nineteenth Century, 16-19
PART II.
I. DEFINITION OF POISON.
35.
14. The LegalDefinition of Poison—English Law as
to Poison, 20, 21
15. German Law as to Poisoning—French Law as
to Poisoning, 21, 22
16. Scientific Definition of a Poison—The Author’s
Definition, 22, 23
II. CLASSIFICATION OF POISONS.
17. Foderé’s, Orfila’s, Casper’s, Taylor’s, and Guy’s
Definition of Poisons—Poisons arranged
according to their Prominent Effects, 23, 24
18. Kobert’s Classification, 24, 25
19. The Author’s Arrangement, 25-28
III. STATISTICS.
20. Statistics of Poisoning in England and Wales
during the Ten Years 1883-92—Various Tables, 28-31
21. German Statistics of Poisoning, 31-33
22. Criminal Poisoning in France, 33, 34
IV. THE CONNECTION BETWEEN TOXIC ACTION
AND CHEMICAL COMPOSITION.
23. The Influence of Hydroxyl—The Replacement
of Hydrogen by a Halogen—Bamberger’s
Acylic and Aromatic Bases, 35, 36
24. The Replacement of Hydrogen by Alkyls in
Aromatic Bodies, 36-38
25. The Influence of Carbonyl Groups, 39
26. Oscar Loew’s Theory as to the Action of
Poisons, 39-41
27. Michet’s Experiments on the relative Toxicity
of Metals, 41, 42
36.
V. LIFE TESTS:OR THE IDENTIFICATION OF
POISON BY EXPERIMENTS ON ANIMALS.
28. The Action of Poisons on Infusoria,
Cephalopoda, Insects, 42-44
29. Effect of Poisons on the Heart of Cold-blooded
Animals, 44, 45
30. The Effect of Poisons on the Iris, 45, 46
VI. GENERAL METHOD OF PROCEDURE IN
SEARCHING FOR POISON.
31. Concentration in a Vacuum—Drying the
Substance—Solvents—Destruction of Organic
Matter, 46-50
32. Autenrieth’s General Process—Distillation—
Shaking up with Solvents—Isolation of Metals
—Investigation of Sulphides Soluble in
Ammonium Sulphide—of Sulphides Insoluble
in Ammonium Sulphide—Search for Zinc and
Chromium—Search for Lead, Silver, and
Barium, 50-53
VII. THE SPECTROSCOPE AS AN AID TO THE
IDENTIFICATION OF CERTAIN POISONS.
33. The Micro-Spectroscope—Oscar Brasch’s
Researches of the Spectra of Colour Reactions
—Wave Lengths, 54-56
Examination of Blood or of Blood-Stains.
34. Naked-eye Appearance of Blood-Stains—
Dragendorff’s Process for Dissolving Blood, 56, 57
35. Spectroscopic Appearances of Blood—
Spectrum of Hydric Sulphide Blood—of Carbon
Oxide Hæmoglobin—Methæmoglobin—of Acid
57-62
37.
Hæmatin—Tests for COBlood—Piotrowski’s
Experiments on CO Blood—Preparation of
Hæmatin Crystals—The Guaiacum Test for
Blood,
36. Distinction between the Blood of Animals and
Men—The Alkalies in various Species of Blood, 62, 63
PART III.—POISONOUS GASES:
CARBON MONOXIDE—CHLORINE—
HYDRIC SULPHIDE.
I. CARBON MONOXIDE.
37. Properties of Carbon Monoxide, 64
38. Symptoms—Acute Form—Chronic Form, 64-66
39. Poisonous Action on the Blood—Action on the
Nervous System, 66, 67
40. Post-mortem Appearances, 67
41. Mass Poisonings by Carbon Monoxide—The
Leeds Case—The Darlaston Cases, 67-70
42. Detection of Carbon Monoxide—The Cuprous
Chloride Method—Wanklyn’s Method—
Hempel’s Method, 70, 71
II. CHLORINE.
43. Chlorine; its Properties—The Weldon Process
of manufacturing “Bleaching Powder,” 71, 72
44. Effects of Chlorine, 72
45. Post-mortem Appearances, 72
46. Detection of Free Chlorine, 72
38.
III. HYDRIC SULPHIDE(SULPHURETTED
HYDROGEN).
47. Properties of Hydric Sulphide, 72, 73
48. Effects of breathing Hydric Sulphide—Action
on the Blood—The Cleator Moor Case, 73, 74
49. Post-mortem Appearances, 74
50. Detection, 74
PART IV.—ACIDS AND ALKALIES.
Sulphuric Acid—Hydrochloric Acid—Nitric Acid—
Acetic Acid—Ammonia—Potash—Soda—Neutral
Sodium, Potassium, and Ammonium Salts.
I. SULPHURIC ACID.
51. Varieties and Strength of the Sulphuric Acids
of Commerce—Properties of the Acid—
Nordhausen Sulphuric Acid, 75, 76
52. Properties of Sulphuric Anhydride, 76
53. Occurrence of Free Sulphuric Acid in Nature, 76
54. Statistics—Comparative Statistics of different
Countries, 76, 77
55. Accidental, Suicidal, and Criminal Poisoning—
Sulphuric Acid in Clysters and Injections, 77, 78
56. Fatal Dose, 78, 79
57. Local Action of Sulphuric Acid—Effects on
Mucous Membrane, on the Skin, on Blood, 79, 80
58. Action of Sulphuric Acid on Earth, Grass,
Wood, Paper, Carpet, Clothing, Iron—Caution
80, 81
39.
necessary in judgingof Spots—Illustrative
Case,
59. Symptoms—(1) External Effects—(2) Internal
Effects in the Gullet and Stomach—Intercostal
Neuralgia, 81-83
60. Treatment of Acute Poisoning by the Mineral
Acids, 83
61. Post-mortem Appearances—Rapid and Slow
Poisoning—Illustrative Cases, 83-85
62. Pathological Preparations in the different
London Hospital Museums, 85, 86
63. Chronic Poisoning, 86
Detection and Estimation of Free Sulphuric Acid.
64. General Method of Separating the Free Mineral
Acids—The Quinine Process—The Old Process
of Extraction by Alcohol—Hilger’s Test for
Mineral Acid, 87, 88
65. The Urine—Excretion of Sulphates in Health
and Disease—The Characters of the Urine
after taking Sulphuric Acid, 88-90
66. The Blood in Sulphuric Acid Poisoning, 90
67. The Question of the Introduction of Sulphates
by the Food—Largest possible Amount of
Sulphates introduced by this Means—Sulphur
of the Bile—Medicinal Sulphates, 90, 91
II. HYDROCHLORIC ACID.
68. General Properties of Hydrochloric Acid—
Discovery—Uses—Tests, 91, 92
69. Statistics, 92, 93
70. Fatal Dose, 93
71. Amount of Free Acid in the Gastric Juice, 93, 94
40.
72. Influence ofHydrochloric Acid on Vegetation—
Present Law on the Subject of Acid
Emanations from Works—The Resistant
Powers of various Plants, 94
73. Action on Cloth and Manufactured Articles, 95
74. Poisonous Effects of Hydrochloric Acid Gas—
Eulenberg’s Experiments on Rabbits and
Pigeons, 95, 96
75. Effects of the Liquid Acid—Absence of
Corrosion of the Skin—Pathological
Appearances—Illustrative Cases, 96, 97
76. Post-mortem Appearances—Preparations in
the different London Museums, 97, 98
77. (1) Detection of Free Hydrochloric Acid—
Günzburg’s Test—A. Villiers’s and M. Favolle’s
Test—(2) Quantitative Estimation, Sjokvist’s
Method—Braun’s Method, 98-101
78. Method of Investigating Hydrochloric Acid
Stains on Cloth, &c., 101, 102
III. NITRIC ACID.
79. Properties of Nitric Acid, 102, 103
80. Use in the Arts, 103
81. Statistics, 103
82. Fatal Dose, 104
83. Action on Vegetation, 104
84. Effects of Nitric Acid Vapour—Experiments of
Eulenberg and O. Lassar—Fatal Effect on Man, 104, 105
85. Effects of Liquid Nitric Acid—Suicidal,
Homicidal, and Accidental Deaths from the
Acid, 105, 106
86. Local Action, 106
87. Symptoms—The Constant Development of Gas
—Illustrative Cases, 106, 107
41.
88. Post-mortem Appearances—Preparationsin
various Anatomical Museums, 107-109
89. Detection and Estimation of Nitric Acid, 109, 110
IV. ACETIC ACID.
90. Symptoms and Detection, 110
V. AMMONIA.
91. Properties of Ammonia, 111
92. Uses—Officinal and other Preparations, 111, 112
93. Statistics of Poisoning by Ammonia, 112
94. Poisoning by Ammonia Vapour, 112
95. Symptoms—Illustrative Case, 112, 113
96. Chronic Effects of the Gas, 113
97. Ammonia in Solution—Action on Plants, 113
98. Action on Human Beings and Animal Life—
Local Action on Skin—Action on the Blood—
Time of Death, 113-115
99. Post-mortem Appearances, 115
100. Separation of Ammonia—Tests, 115, 116
101. Estimation of Ammonia, 116
VI. CAUSTIC POTASH AND SODA.
102. Properties of Potassium Hydrate, 116, 117
103. Pharmaceutical Preparations, 117
104. Carbonate of Potash, 117
105. Bicarbonate of Potash, 117
106. Caustic Soda—Sodium Hydrate, 117, 118
107. Carbonate of Soda, 118
108. Bicarbonate of Soda, 118
109. Statistics, 118
110. Effects on Animal and Vegetable Life, 118, 119
111. Local Effects, 119
42.
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