SMALLPOX AND VACCINATION. 505 



nant cowpox. Sheep-pox also has many clinical and pathological anal- 

 ogies with human smallpox, and facts as to its relation to cowpox 

 vaccination similar to those observed in cattle-plague have been re- 

 ported. 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 Sanderson was 

 among the first to show that in vaccine lymph there were certain bodies 

 which he recognised as bacteria. Since then numerous observatiops 

 . 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. staphylo- 

 coccus 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. Klein, and also, independently, 

 Copeman, have observed an organism in lymph taken from a vaccine 

 pustule in a calf on the fifth and sixth days, in human vaccine lymph on 

 the eighth day, and in lymph from a smallpox pustule on the fourth day. 

 To demonstrate the bacilli, cover-glass films are dried and placed for 

 five minutes in acetic acid (i in 2), washed in distilled water, dried, and 

 placed in alcoholic gentian-violet for from twenty-four to forty-eight 

 hours, after which they are washed in water and mounted. Copeman 

 and Kent also found the bacilli in sections of vaccine pustules stained 

 by LofHer's methylene-blue, or by Gram's method. The organisms are 

 .4 to .8 jii in length, and one-third to a half of this in thickness. They 

 are generally thinner and stain better at the ends than at the middle. 

 They occur in groups of from three to ten in both the lymph and the 

 tissues. In the centre of their protoplasm there is often a clear globule, 

 which is looked on as a spore. They have hitherto resisted the ordi- 

 nary isolation methods, a fact which is rather in favour of their non- 

 saprophytic nature. By inoculating fresh eggs with the crusts of 

 smallpox pustules Copeman has, however, obtained a growth of a bacillus 

 resembling that found by him in the tissues. Though sub-cultures on 

 ordinary media have been obtained, the pathogenic effects of these have 

 not been fully investigated, and thus the identity of this bacillus with 

 that seen in the tissues is not proved. The facts that the latter is one 

 hitherto not recognised microscopically, that it exists in the pustules, the 

 contents of which are probably the means by which the disease naturally 

 spreads, that it resists artificial cultivation, that the possession by it of 

 spores explains some of the characteristics of vaccine lymph (resistance 

 to drying, etc.), are, however, of interest from the point of view of the 

 possible etiological relationship of the bacillus to the disease. 



