4 BABIES 



with basophile granules, rods, and ' circles.' These bodies 

 are from 0.5//, to 20^ in diameter, the size increasing 

 with the time that the disease has run, the larger forms 

 being met with in less susceptible animals, the smaller in 

 specially susceptible animals, and in those cases in which 

 the disease runs a very rapid course. In some cases these 

 bodies may be constricted in the middle, or, if the bodies 

 are somewhat elongated, there may be two or three constric- 

 tions. These bodies may be found in any of the nerve cells 

 of the central nervous system in cases of rabies, but they 

 are most numerous and are found most readily in the cells 

 of Ammon's horn and in the Purkinji cells of the cere- 

 bellum. 



It has been suggested that a small central corpuscle, 

 surrounded by no clear space, may correspond to a proto- 

 zoan nucleus ; this, however, can be little more than a 

 suggestion. The presence of these Negri bodies certainly 

 appears to be specific to rabies and hydrophobia. Such 

 bodies are present in large numbers even at an early stage 

 of the disease, but are then so small that they may easily 

 escape detection ; they may be so small, indeed, that they 

 pass through the pores of a Berkefeld filter. Later, and 

 this of course is best seen in more chronic cases, they 

 attain a considerable size. 



These bodies may be simply the result and not the 

 cause of disease, but many who have examined them 

 acknowledge that they may be protozoan in character. 



Microbes, when cultivated in media containing chemicals, 

 or when repeatedly passed by inoculation through the 

 bodies of certain animals, become weakened, and lose their 

 virulence. Attenuated cultures or vaccines, properly em- 

 ployed, confer on certain animals more or less protection 

 against poisonous doses of the natural virus subsequently 

 introduced by infection, or by experimental inoculation. 

 In districts of France, Russia, Austria, and Switzerland, 

 where anthrax abounds, cattle and sheep for many years 

 have been vaccinated with attenuated anthrax virus, the 

 mortality among the vaccinated is stated to be less than 

 one-tenth of that which occurs amongst the unvaccinated 

 stock. Pasteur, by repeated injection of attenuated rabies 



