REPORT OF THE ROYAL VACCINATION COMMISSION. 671 



incapable of taking that disease ; the insusceptibility being shown on the 

 one hand by the failure to contract the disease after ample exposure to 

 contagion, such as nursing and attending to or even sleeping with persons 

 suffering from small-pox, and on the other hand by the fact that when 

 the person in question was inoculated with the matter of small-pox in the 

 manner then usual (the matter being tested as to its efficiency on 

 susceptible persons) the inoculation failed to excite small-pox. In the 

 course of the inoculation practice it had been observed that when the 

 operation was performed upon a person who had already had small-pox, 

 either naturally or by inoculation, the wound of inoculation, instead of 

 developing, as it did when the operation was successful in a person who 

 had not had the small-pox, into a vesicle and so into a pustule with the 

 variolous characters (the development being accompanied by febrile 

 symptoms and, save in exceptional cases, by the appearance of a smaller 

 or greater number of variolous pustules on parts of the skin other than 

 the seat of inoculation), presented as a rule nothing more than some slight 

 inflammation, dying away in a few days without any other symptom, or even 

 healed at once without any symptoms at all, local or general ; and in the 

 exceptional cases in which further changes took place in the wound, these 

 were not accompanied or followed by an eruption of pustules or even by 

 the febrile and other general symptoms of small- pox. Accordingly, in 

 cases of small-pox inoculation where it was doubtful whether the disease 

 had been communicated, it had become not an uncommon practice to 

 repeat the operation, in order to judge by the effects produced whether 

 the earlier inoculation had or had not produced the disease ; and the 

 practice, thus originating in connexion with small-pox inoculation, had 

 come to be spoken of as the " variolous test." 



In his treatise Jenner distinguishes between what he calls true cow-pox 

 and other eruptions which he speaks of as spurious, and which he regarded 

 as not affording protection against small-pox, although he gives no details 

 to show that the cases quoted by him as affording protection were cases 

 of his true cow-pox. He also developed the view that matter derived from 

 horses suffering from the disease known as the grease is capable of giving 

 rise to cow-pox in the cow, and indeed is the real origin of the true 

 disease. It may be added that Jenner also expressed the opinion that the 

 protection thus afforded by cow-pox was permanent in character. 



Jenner further recorded in the same treatise how he had in 17% 

 inoculated a healthy boy of eight years of age in the arm with cow-pox 

 matter taken from a sore on the hand of a dairymaid who had been 

 infected with the disease by milking cows suffering from cow-pox. He 

 describes the appearances subsequently presented by the wounds, and 

 states that, six weeks afterwards, the results of inoculating the boy with 

 variolous matter were those commonly seen to follow the inoculation of 

 persons who had previously had the cow-pox or the small-pox : that is 

 to say, the " variolous test" showed the boy to be insusceptible to small- 

 pox. Some months afterwards the boy was again inoculated, but no 

 sensible effect was produced on the constitution. Jenner then relates that 

 subsequently, in the spring of 1798, he inoculated a child, and obtained a 

 similar result with matter taken directly from the nipple of a cow infected 



