THE EPIZOOTIC DISEASES TN HORSES, CATTLE, &C. 341 
live process. This humidity has an injurious effect on all kinds 
of animals that have a weak and lymphatic temperament, among 
which are the ruminants. Sheep are in the unfavourable situa- 
tion of most quickly receiving this impression. That which took 
place in 1816 affords a lamentable example of it. The rain 
continued to pour during the whole of the summer; and in con- 
sequence of this, almost every flock, even those that were best 
taken care of, became a prey to dropsy, which prevailed epizooti- 
cally from the commencement of autumn. 
“ Humidity in excess aggravates the inconvenience both of cold 
and heat, and establishes a state of the atmosphere favourable 
to the production of the most destructive diseases. Epizootics 
do not, however, always proceed from this cause; but in addition 
to the too fatal disposition to imbibe this atmospheric influence, 
there comes the fatal principle of contagion , and here its ravages 
are exhibited on a dreadfully extensive scale. The theatre on 
which this principle develops its fatal influence is often most 
extensive, or, in fact, it is boundless. This is the case in many 
of the varieties of typhus to which cattle are exposed. There are 
historical records of its having more than once pervaded the whole 
of Europe, and, indeed, extended almost over the known world. 
“ In these dreadful circumstances, in which death claims so 
great a number of victims, medicine can furnish but little aid. 
The unknown origin and character of the disease is a most seri- 
ous evil. It places the practitioner in a state of darkness and of 
doubt, which can only be dissipated by the light of experience, 
and experience of such a nature and to such an extent as rarely 
falls to the lot of any one. The earlier victims of the disease 
could not, at all events, benefit by it ; and it is too rare that the 
veterinarian is consulted until the malady is confirmed, and its 
victims become numerous. They who first observe the change 
in the appearance of the animal are generally persons of little or 
no education. They see in the disease nothing but the effect of 
some trifling cause, of the existence of which they have never 
any doubt. The death of the animal is in their estimation per- 
fectly accidental; it is only a local and an individual loss, and 
there is nothing about it to excite any general interest. 
“ Comparative pathology can offer some useful contributions to 
the science of general medicine, and, under this relation, is de- 
serving of the regard of the human practitioner. Many celebrat- 
ed professors of human medicine have not disdained to occupy 
themselves with the epizootics that have prevailed around, and 
they have always rendered eminent service in these seasons 
of public calamity. A medical man who regards himself as above 
inquiries or observations of this kind, being placed in a locality 
VOL. XIV. Y y 
