504 SMALLPOX AND VACCINATION. 



(resistance to drying, etc.), make its further investigation a 

 matter of considerable interest. 



Various observers have described appearances in the 

 epithelial cells in the neighbourhood of the smallpox or 

 vaccine pustules, which they have interpreted as being 

 protozoa. Thus Ruffer 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 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 appear to multiply by 

 simple division, and in the living condition exhibit amoeboid 

 movement. Similar bodies have been described by Reed 

 in the blood of smallpox patients and of vaccinated children 

 and calves. The significance of such appearances is 

 unknown. 



The Nature of Vaccination. As we are ignorant of 

 the cause of smallpox, we can only conjecture what the 

 nature of vaccination is. From what we know of other 

 like processes, however, we have some ground for believing 

 that it consists in an active immunisation by means of an 

 attenuated form of the causal organism. As to how im- 

 munity is maintained after vaccination, we do not know 

 much. Some, including Beclere, Chambon, and Menard 

 (who jointly investigated the subject), maintain that in the 

 blood of vaccinated animals substances exist which, when 

 transferred to other animals, can confer a certain degree of 

 passive immunity against vaccination, and which have also 

 a degree of curative action in animals already vaccinated. 

 Beumer and Peiper, on the other hand, could not find 

 evidence of the existence of such bodies. If they do 

 exist, we cannot as yet say whether they are antitoxic or 

 antimicrobic. 



