BACTERIA IN SMALLPOX ' 569 



cultures or the products of such. In the absence of this 

 evidence we are at present justified in considering that there is 

 strong reason for believing that vaccinia and variola are the same 

 disease, and that the differences between them result from the 

 relative susceptibilities of the two species of animals in which 

 they occur naturally. 



With regard to the relation of cowpox to horsepox, it is 

 extremely probable that they are the same disease. Some 

 epidemics of the former have originated from the horse, but in 

 other cases such a source has not been traced. Cattle plague 

 fnmi the clinical standpoint, and also from that of pathological 

 anatomy, resembles very closely human smallpox. Though 

 each of the two diseases is extremely infectious to its appropriate 

 animal, there is no record of cattle-plague giving rise to small- 

 pox in man or vice versa. When matter from a cattle-plague 

 pustule is inoculated in man, a pustule resembling a vaccine 

 pustule occurs, and further, the individual is asserted to be now 

 immune to vaccination ; but vaccination of cattle with cowpox 

 lymph offers no protection against cattle-plague, though some 

 have looked on the latter as merely a malignant cowpox. Sheep- 

 pox also has many clinical and pathological analogies with 

 human smallpox, and facts as to its relation to cowpox vaccina- 

 tion similar to those observed in cattle-plague have been 

 reported. Smallpox, cowpox, cattle-plague, horsepox, and sheep- 

 pox, in short, constitute an interesting group of analogous 

 diseases, of the true relationships of which to one another we 

 are, however, still ignorant. 



Micro-organisms associated with Smallpox. Burdon Sander- 

 son and other observers early pointed out that in matter derived 

 from variolous and vaccine pustules (especially the later stages 

 of the latter), pyogenic organisms are always present, e.g. 

 mtaphylococcuz aureus and staphylococcus cereus Jlavus, and many 

 of the ordinary skin saprophytes also are often present, but no 

 organism has ever been isolated which on transference to animals 

 lias been shown to have any specific relationship to the disease. 

 Streptococci have also been described as agglutinable by the sera 

 of smallpox patients and of vaccinated persons ; such sera, it may 

 be said, had no effect on other strains of streptococci. Calmette 

 and Guerin have described very minute granules in the lymph 

 \\hirli could not be cultivated, but which persisted after all the 

 bacteria had been removed. (The method by which the latter 

 was accomplished was by exciting a leucocytosis in a rabbit's 

 l>eritoneum and then introducing the vaccinal lymph ; the 

 leucocytes phagocyted the bacteria so that the lymph no longer 



