HUMAN AND ANIMAL VARIOLAS 
187 
tion, take that which is directly elaborated in cows through inocu¬ 
lation with the small-pox matter of man, and thus save all the 
search and precautions at present imposed upon us in order to 
obtain a vaccine fluid which shall be innocuous, and at the same 
time sufficiently potent to afford protection from variola. But 
if, on the contrary, the small-pox communicated to the cow re¬ 
tains all its characters, and when again transferred to mankind 
merely reproduces itself in its dangerous, general eruptive and 
highly infectious form, then recourse to variolo-vaccination would 
be a serious and reprehensible step, and one which should be op¬ 
posed. Or if the small-pox virus, in passing through the cow, 
should still retain its variola-producing attributes, but yet become 
so subdued as to be as harmless, and still as effective as vaccine, 
ought it to take the place of the latter altogether, or should it be 
employed simply as an auxiliary ? These questions have been asked 
before, and I venture to ask them again, as a reply to them is of 
the greatest moment at this particular time, not only in regard to 
small-pox, but to other virulent affections. For if, notwithstand¬ 
ing the apparent differences in their characters, the human and 
bovine diseases are the same in nature, the virus only being bene¬ 
ficially modified or transformed by transference from the one 
creature to the other, it gives us reason to hope that the virulent 
principle of other contagious scourges which only attack once in a 
lifetime, may be similarly attenuated by emigration from one 
species of animal to another, and still retain its protective influ¬ 
ence. But if the human and the cow disease are due to a differ¬ 
ent virus, and the one has power to neutralize the other, the 
reciprocal neutralization being greatly to the advantage of the 
creatures concerned, then also there is good reason for hoping 
that with other contagious maladies of the same, or even a differ¬ 
ent type, there may be discovered a similar means of destroying 
their germinative power. 
Notwithstanding the immense importance of the question, the 
long time that has elapsed since vaccination was introduced, the 
multitude of works upon the diseases, and the great opportuni¬ 
ties that have been afforded for clinical and experimental obser„ 
vation, it is indeed astonishing to find opinions still divided on 
