NATURE OF VACCINATION 509 



have been looked on by many as protozoa, and Guarnieri himself 

 stated that multiplication could be seen occurring in them in 

 fresh lymph, but Ewing and also Prowazek have brought forward 

 strong evidence for the appearances being due to nuclear changes, 

 Still the question of the specificity of these changes to variolous 

 lesions remains, and here it may be said Wasielewski has shown 

 that they persist through 46 transfers on the cornea of the 

 rabbit and further no similar appearances have been found in 

 other skin lesions. Prowazek examined material fixed in a hot 

 mixture of two- thirds saturated perchloride of mercury and 

 one -third 90 per cent, alcohol, washed in 40 per cent, iodine 

 alcohol and stained in Grenacher's haematoxylin, and found 

 bodies in the epithelial cells 1-4 fj. in size, sharply contoured 

 and having ragged edges as if made up of massed chromosomes. 

 These were often broader at one end than at the other, and 

 appearances have been seen which suggest longitudinal division. 

 Prowazek has also seen these " lymph-bodies " as he has called 

 them in the lymph, and he inclines to the idea that they may be 

 protozoa. Bonhoff and also Carini have described spirochaetes 

 as occurring in variolous lesions, but this has not been confirmed. 

 Future investigations must show what significance is to be 

 attached to these various observations. 



The causal organism of smallpox is probably very small as, 

 though there has been some difference in opinion on this point, 

 there is little doubt that it will pass through the coarser porcelain 

 filters. 



The Nature of Vaccination. As we are ignorant of the cause 

 of smallpox, we can only conjecture what the nature of vaccina- 

 tion 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 immunity 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. 



