BACTERIA IN SMALLPOX 507 



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 naturally occur. 



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 

 from 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 was among the first to show that in vaccine lymph there 

 were certain bodies which he recognised as bacteria. Since 

 then numerous observations have been made as to the occurrence 

 of such in matter derived from variolous and vaccine pustules. 

 In especially the later stages of the latter, many of the pyogenic 

 organisms are always present, e.g. staphylococcus aureus and 

 staphylococcus cereus flavus, and many of the ordinary skin 

 saprophytes also are often present, but no organism has ever 

 been isolated which on transference to animals has 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 which could 

 not be cultivated but which persisted after all the bacteria had 

 been removed. (The method by which the latter was accom- 

 plished was by exciting a leucocytosis in a rabbit's peritoneum and 



