PREFACE 
At the time of writing this book, there has been no attempt to present 
the study of viruses as the separate discipline of—to use a bastard 
word—virology. Heretofore, the subject has been divided up into 
artificial compartments, plant viruses, animal viruses, and bacterio- 
phages, as if there were no common bond between them. I have 
therefore attempted to survey the whole field, superficially no doubt, 
but in such a way that the relationships between these interesting 
agents may become clear to the student. In doing this I am aware 
that I am inviting criticism and that there may be little in common 
between, say, the viruses of vaccinia or psittacosis and some of the 
very small plant viruses. We can, however, follow Boycott’s 
suggestion of a descending scale with the smallest organisms at one 
end and the protein molecule at the other. In between those limits, 
and perhaps overlapping at each end, lie the viruses, a heterogeneous 
collection no doubt but all showing some characteristics in common. 
Like most modern scientific disciplines, but more so than some, 
the study of viruses becomes essentially a matter of team work because 
of its many contacts with other subjects and its wide ramifications 
through much of the field of natural science. This makes it a difficult 
matter for one writer to cover the field in an adequate, if only intro- 
ductory, manner and a severe test of his comprehension of the subject. 
I have, nevertheless, written this book in the hope that it will be of 
use, not only to the “‘virologist,” if such a person exists, but also to 
the biochemist, the biologist, the medical student and anyone else 
who is interested in that borderland country whose boundaries were 
described by Aristotle as “indistinct and doubtful.” 
Grateful acknowledgment is due to my colleague, Dr. Roy 
Markham, for his constructive criticism of Chapters V to VIII, and for 
taking many of the photographs used in the illustrations. 
K. M. S. 
