706 INFLUENCE OF CHOLERA ON THE LOWER ANIMALS. 
tion of a predisposition to contagious diseases, I hold to be 
one of the chief elements of success in experimentation on 
the transmissibility of cholera to animals. The chief features 
of the laws of the diffusion of epidemic cholera in man must 
also be borne in mind : for instance, its unequal and partial 
distribution — its attacking places characterised by certain 
conditions of temperature, moisture, drainage, &c. — its 
varying duration — its course, in opposition to ordinary phy- 
sical laws, &c. 
We are not to look, in epizootic cholera, for all the symp- 
toms of human cholera, as laid down in systematic treatises 
or text-books. Even in man, the conventional symptoms 
are frequently absent; and the only one which can be said 
to be invariable, and hence essential, is collapse. In propor- 
tion as cholera is becoming domesticated among us, so do we 
find its types and symptoms undergoing modification ; and, 
if such be the case in man, how much less should we ex- 
pect to find the same symptoms in animals differing essen- 
tially from him in structure, habits, and food? In propor- 
tion, however, as an animal resembles man in the structure 
of its digestive apparatus, in the nature of its food, and in its 
habits, so shall we expect to find the characters of the disease 
resembling those in the human subject. Thus we shall find 
the dog — man’s most constant companion — one of the best 
subjects in which to study the cholera of the lower animals. 
The symptomatology of epizootic diseases is somewhat 
puzzling, and liable to lead into error. For instance, cases of 
sudden death are common in cattle and other ruminants, pro- 
ceeding from acute intestinal lesions ; while many symptoms, 
resembling isolated or individual symptoms of cholera in man, 
such as cramps, vomiting, thirst, and diarrhoea, are very 
common as symptomatic of mild affections in some of the 
lower animals, such as the dog. The absence and presence 
of particular symptoms are thus alike delusive; hence, 
nothing can atone for a deficiency in accurate observation, 
especially in pathological examination. The subject of cho- 
lera in the lower animals cannot be perfectly understood 
without a knowledge of other epizootic diseases; while, 
again, for the satisfactory investigation of the latter, a. fami- 
liarity with the ordinary sporadic diseases to which the 
lower animals, domesticated and wild, are subject, is neces- 
sary. The study of epizootic cholera by medical practitioners 
would probably give a stimulus to the study of veterinary 
medicine, and lead especially to a greater cultivation of vete- 
rinary pathology, some departments of which bear specially 
on our present subject. Among other points in the patho- 
