608 SMALLPOX AND VACCINATION 



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 vacci- 

 nation 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. 



The Virus of Smallpox and Vaccinia. — Burdon-Sanderson 

 and others early pointed out that in the discharge of variolous 

 and vaccine pustules — especially in the later stages — pyogenic 

 organisms are present and ordinary skin saprophytes also occur. 

 Klein and Copeman described a bacillus which was difficult to 

 cultivate, but no organism has ever been isolated from the 

 characteristic lesions which, on transference to animals, has been 

 shown to produce specific effects. The adventitious bacteria 

 present in lymph are usually removed or reduced in numbers by 

 .emulsifying it with glycerine before use. Calmette and Guerin 

 removed these organisms by subjecting them to phagocytosis in 

 the rabbit's peritoneum, and found in the bacterium-free lymph 

 very minute granules, which, however, resisted attempts at 

 cultivation. Such a material still produces vaccinia, and the 

 same effect is obtained with lymph passed through a Berkefeld 

 filter, so that the infective agent must be of great minuteness 

 and is to be grouped with the filterable viruses. Noguchi has 

 obtained results similar to those of the French observers by 

 passage of the virus through the testicle in a series of rabbits. 



Various observers have described structures in the epithelial 

 cells in the neighbourhood of the smallpox or vaccine pustules, 

 which they have interpreted as being protozoa. Thus Buffer 

 and Plimmer describe as occurring in clear vacuoles in the cells 

 of the rete Malpighii at the edge of the pustule (in paraffin 

 sections of vaccine and smallpox pustules carefully hardened in 

 alcohol, and stained by the Ehrlich-Biondi mixture) small round 

 bodies of about four times the size of a staphylococcus pyogenes, 

 coloured red by the acid fuchsin, sometimes with a central part 

 stained by the methyl-green. These are described as multiplying 

 by simple division, and in the living condition exhibiting 

 amoeboid movement. Similar bodies have been described by 

 Beed in the blood of smallpox patients and of vaccinated 

 children and calves. 



These are probably the bodies described by Guarnieri, and to 



