1902.] The Inter -relationship of Variola and Vaccinia, 123 



present paper, my attempts at direct transference of human small-pox 

 material to the calf met with no s access. 



All my earlier experiments were conducted at the Brown Institution, 

 in order to avoid any possibility of contamination with vaccinia. As 

 a further precaution new scalpels were used, which were invariably first 

 carefully sterilised in the flame of a spirit lamp, and, after use, the 

 table was, on each occasion, thoroughly washed with carbolic acid 

 (1 in 20), while during the intervals of use it was kept exposed to 

 the air under an open shed. Similar precautionary measures have 

 been observed throughout the course of my later work. 



The difficulty experienced by myself and the numerous other investi 

 gators, to whom reference has already been made, in attempts to 

 transmit human small-pox directly to bo vines, whether cows or calves, 

 is not infrequently cited as a reason for regarding with distrust the 

 theory expounded by Jenner, that cow-pox, whether carried through 

 the horse as intermediary host or not, was originally derived from 

 small-pox in the human being. 



But a great deal, at any rate, of the small-pox which was preva- 

 lent at the time that Jenner lived and wrote was of that compara- 

 tively mild variety which, under the name of inoculated small-pox, 

 was intentionally produced in healthy subjects, with the object of 

 thereby conferring protection against subsequent attack by the disease 

 in virulent form. 



So mild indeed at times were the results of inoculations in the hands 

 of such operators as Adams and the brothers Sutton that, as we learn 

 from contemporary records, in many instances but little obvious effect 

 was observed, with the exception of the local vesicle arising at the site 

 of insertion of the small-pox virus, and the patients suffered but little 

 inconvenience. Thus, more particularly in certain of Adams' cases, as 

 may be gathered from his own account of the circumstances, the visible 

 effect produced so closely resembled the results then beginning to be 

 known as following on the Jennerian process of vaccination, that 

 numbers of his patients were with difficulty persuaded that he had not, 

 contrary to their desire, intentionally vaccinated rather than variolated 

 them. The gradual evolution of a strain of lymph of such tenuity, 

 according to Adams himself, was obtained by attention to the mode of 

 life and general treatment of persons undergoing the process, together 

 with careful selection of the sources (preferably the primary vesicle) 

 from which the virus was obtained. 



The majority of persons thus inoculated are not likely to have been 

 incapacitated, as the result of the operation, to a much greater extent 

 than are those who undergo efficient vaccination at the present day, 

 and doubtless, therefore, they would be, for the most part, capable of 

 following their ordinary avocations during the progress of the induced 



