Some Relations of Biolotjij to Agricultin-e. 
433 
than one who is familiar with the striking peculiarities of this affection 
in cattle, sheep, swine, fowls, and other animals. 
Especial importance necessarily attaches to the study of such dis- 
eases as are communicable from animals to man, as, for instance, 
glanders, anthrax, tuberculosis, many entozoic affections, itc. ; and, in 
general, these are the animal diseases which h.ive received the most 
attention from students of human pathology. The experimental pro- 
duction of diseases in the lower animals affords an insight, to be 
gaiiaed in no other way, into the causes, development, lesions, and 
functional manifestations of many disorders. Experience, however, 
has shown that grave errors are likely to be committed by experi- 
mental pathologists who have no knowledge of the natural diseases 
and conditions of the animals used for experimentation. Often, for 
example, those studying the question of experimental tuberculosis 
have mistaken for genuine tubercles the nodules produced by parasitic 
entozoa, and have thus been led to form misleading conclusions. 
An important and promising field of pathological study is to be 
found in the infectious diseases of animals and of plants, not only on 
account of the great economic interests often involved, but also be- 
cause it affords a means of widening and deepening our conceptions 
as to the causes, development, prevention, and treatment of infectious 
diseases in general. Any pathologist who is at all familiar with the 
remarkable and peculiar conditions, under which the so-called Texas 
cattle fever of the United States develops and spreads, will realise 
that the complete elucidation of all the etiological factors of this dis- 
ease would not only contribute to the solution of a great economical 
problem, but would also open fresh points of view in our conceptions 
of infectious agents and their properties. It is not a small thing that 
questions which were once considered to be wholly transcendental, as, 
for instance, the doctrine of immunity against infectious diseases, 
should have been brought within the working domain of experimental 
pathology. The interesting studies of heredity by Weismann and 
others pertain in part to pathology, and also illustrate forcibly the 
value of the comparative method of research. 
The S])orozoa. — In discussing the pathogenic {i.e. disease-pro- 
ducing) Sporozoa, Professor Ramsay Wright, of the University of 
Toronto, stated that the Sporozoa are a group of low forms of 
animal life, belonging to the sub-kingdom Protozoa, which, in 
consequence of the universal adoption of a parasitic mode of life, 
possess certain peculiarities of structure and reproduction which 
mark them off quite sharply from the rest of the sub-kingdom. 
The structural peculiarities consist chiefly in the absence of any 
specialised organs for locomotion, or for the ingestion of food, 
whilst the reproductive peculiarities are found in the formation of 
large numbers of characteristic spores — whence the name Sporozoa, 
given by Leuckart. They are all unicellular animals, occasionally 
so large as to be visible to the unaided eye, but often — especially 
those of pathological interest — quite microscopic. Four orders 
distinguished : (1) Gregarinidia, (2) Sarcosporidia, (3) Myxpr 
