290 
ON THE TKANSMISSION OF DISEASES 
his wrist. This eruption was seen by some medical men, who, 
struck with the great resemblance of the pustules to those of cow- 
pox, inoculated two infants with the matter which they con¬ 
tained. True cow-pox supervened in both of them, and the 
matter taken from the pustules served for many subsequent 
vaccinations. 
Other experiments, however, made at the same time and with 
the same view, were far from confirming the opinion of Jenner 
and Godine. In order to remove every doubt as to the produc¬ 
tion of cow-pox by the matter of grease, it was necessary to insti¬ 
tute other experiments—to vary them—to note the intensity of 
the disease, and the character of the matter used and produced. 
Without these precautions the public mind would have long con¬ 
tinued in doubt. 
Whatever was the result of these experiments, it may be use¬ 
ful to observe that this disease in the cow is dependent on various 
atmospheric influences, on the humidity of the soil, on the expo¬ 
sure to certain winds, &c., and that it appears on many farms on 
which no horses are kept*. 
Every one knows that rabies—that most fearful disease—may 
be spontaneously developed in some of the carnivora, as the dog, 
the wolf, &c. That these animals can, by their bite, transmit 
the same disease to the human being, we have too numerous 
proofs. The rabid virus appears to reside in the saliva, or 
* Dr. Jenner undoubtedly believed that the sanious fluid of grease was 
the original virus, and that the cow-pox in the cow itself was nothing more 
than a casual inoculation produced by her lying down in a meadow in 
which a greasy horse had been previously feeding, and her udder coming in 
contact with the discharge that had dropped there. 
Dr. George Gregory, so late as the year 1825, in his Practice of Physic^ 
says that “it is highly probable that the cow-pox is only a secondary disease 
in cows; that, originally, it is an affection of the hoof of the horse com¬ 
municable to man directly, or to him through the cow. It has, however, 
been proved beyond doubt, that cow-pox has been found when the attend¬ 
ants on the cows could have had no communication with greasy horses, nor, 
in fact, with any horse, sick or well, and where the cows had no access to 
pastures on which horses had been fed for many years before.” 
Some medical men may reason from most imperfect information or ana¬ 
logy ; but I believe that there is no veterinary surgeon, whose life is spent 
amidst these diseases, who believes that there is the slightest connexion 
between cow-pox and grease. Still, however, there is one undoubted fact, 
that from time immemorial, farriers and blacksmiths that have been infected 
by grease, have been considered unsusceptible of variolous contagion; but 
this only proves that there may be other animal poisons possessing the pre¬ 
servative power of the vaccine matter. There is no connexion between the 
two, and while the matter of cow-pox does its duty with such unvarying 
certainty and with so little danger and disturbance of the system, we shall 
not trouble ourselves to look for other preventives.—Y. See Good's 
Study of Medicine^ vol. iii, p. 59, and Youatt on Cattle, p. 556. 
