464 SMALLPOX AND VACCINATION. 



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 in so many conditions that as yet it is impossible 

 to assign any specific significance to them. 



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. 



