682 SUPPLEMENTARY APPENDIX. 



in the cow gave rise to a specific efEect which was not cow-pox but was 

 of the nature of small-pox, though its manifestations in the cow were 

 different from those of small-pox in man. They also obtained similar 

 results in attempting to transfer small-pox to the horse. 



It must be admitted that the results finally obtained in some of the 

 successful cases were indistinguishable from those of vaccination ; the 

 characters of the local vesicle, the absence of eruptive pustules and of 

 contagiousness, show that the lymph thus apparently originating from 

 small-pox in the hands of Oeely, Badcock, and others, was vaccine lymph. 

 It has been urged that a vaccine vesicle making its appearance in the 

 wound of inoculation with small-pox was due to the accidental intro- 

 duction of cow-pox matter into the wound ; the small-pox matter in 

 the wound produced no effect, and the cow-pox matter its usual efEect. 

 Several considerations support this view. The cow is peculiarly suscep- 

 tible to cow-pox. In some cases (Oeely, Voigt), the animal was 

 vaccinated as well as inoculated with small-pox : thus, in Ceely's first 

 case, the animal was inoculated with small-pox on one side of the body, 

 and a few days after vaccinated on the other side. In many cases the 

 experiments were conducted in an animal vaccine establishment, the 

 stalls, the operating tables, and the assistants being those used or engaged 

 in vaccination. It is true that in some cases at least special precautions,, 

 sterilisation of instruments and the like, were taken to avoid the accidental 

 introduction of cow-pox ; but in observations of this kind the difliculties 

 of avoiding all such sources of error are notorious. Still the successful 

 cases are now so numerous that it is difficult to resist the conclusion that 

 the same accident could not have occurred in all, and that a transformation 

 of small-pox into cow-pox — that is to say, into the artificially inoculated 

 cow-pox which we call vaccine * — really took place. 



Accepting this view provisionally, it may be remarked that in most 

 cases the transformation was sudden and complete ; the small-pox virus, 

 under the influence of the tissues of the cow, became immediately 

 converted ipto vaccine virus, and this produced a typical vaccine vesicle. 

 In some cases {ex. gr., that of Hime) the transformed virus produced its 

 effect not iu the wound of inoculation, or not chiefly so, but at some little 

 distance from it. In some cases the characters of the vesicle first formed, 

 though sufBciently distinct to justify the vesicle being called a vaccine 

 vesicle, were not those of a perfecft vaccine vesicle, but the lymph from 

 such a vesicle, at least after one or two removes, gave rise to most typical 

 vaccine vesicles. 



In Klein's experiments the transformation was gradual. In his fourth 

 cow, the virus was as yet not typical vaccine, since it did not produce a 

 typical vesicle ; yet it was so far already vaccine that, transferred to the 

 child, it produced typical vaccine (unless we suppose some accidental 

 introduction of vaccine to have taken place). That the vesicle on the 

 child was vaccine, and not small-pox unaccompanied by eruptive pustules, 

 was shown not only by its characters but also by the fact that lymph from 

 it produced typical vaccine in the cow. 



In Chauveau's experiments no transformation at all took place. 



* The italics are mine. —E.M.C. 



