The term “variolæ vaccinæ” employed by Jenner, as a synonym for cow-pox, has been generally accepted as affording evidence that in so naming this disease, “small-pox of the cow,” he was desirous of placing on record his belief that cow-pox, or vaccinia, was intimately related to human small-pox, if indeed it were not directly derived from it. This theory, however, appears to have found but scanty favour in Jenner’s day, and even at the present time the value of the practice of vaccination is, by some, impugned on the plea that inoculation of one disease—cow-pox—could not be expected to exert any really protective influence against the ravages of small-pox—a disease considered by them of totally different origin.