De Zouche. — Bacteria a)id their Relation to Discafie. 53 



trtxi-y case, as in malignant scarlatina and malignant cholera, 

 he dies. 



(3.) The answer to the question as to the cure or pre- 

 vention of a zymotic disease by vaccinating with attenuated 

 virus may now be perceived. On such theories or facts is 

 founded M. Pasteur's treatment of hydrophobia; and it is 

 claimed that anthrax, typhoid, and septicaemia can be pre- 

 vented by injecting into the blood some of their poisonous 

 products. The presence of these substances in the blood 

 alters it in such a way as to render it an unfit soil for the 

 growth of the respective bacteria. The white cells do not 

 always at first take up virulent bacteria, but sometimes with- 

 di'aw from them ; i)ut they can gradually become accustomed 

 to some poisonous bacteria, and are able to devour and digest 

 them if they are first fed with the attenuated virus. 



We will now glance at a few of the specific bacteria. The 

 first microbe discovered as the cause of disease was, as al- 

 ready mentioned, the bacillus of anthrax. Its life-history is 

 therefore invested with peculiar interest, for the demonstra- 

 tion of its presence and of its infecting-power was immediately 

 followed by a search for specific bacteria in other diseases. 



Bacillus aiithracis is interesting on its own account, for 

 it is one of the most malignant of the bacteria, and is capable 

 of retaining its virulence under the most varied circumstances. 

 It can grow in living matter, in dead matter, animal or vege- 

 table. It may preserve its vitality after being frozen in a 

 fluid at —110° C, and the spores may be capable of germina- 

 tion after being boiled for from fifteen minutes to an hour. 

 M. Pasteur found the germs capable of development after they 

 had been kept twenty-two years. Its spores defy the 

 solvent powder of the gastric juice. It is capable of attack- 

 ing rodents, ruminants, omnivora, carnivoi-a, birds, and even 

 batrachians and reptiles under certain conditions of tem- 

 perature. Mice and guinea-pigs die in from twenty-four to 

 forty-eight hours after infection with the minutest quantity 

 of virus, and if a drop of blood be examined anthrax rods 

 will be found, so rapid is the growth of the microbe. Man 

 does not escape: anthrax, or charbon, in nian is known as 

 woolsorters' disease. The spot which it attacks imme- 

 diately developes a pustule which is well characterized by the 

 term " malignant pustule." We have here a striking example 

 of a vicious heredity ; but, on the other hand, we have a remark- 

 able instance of the manner in which a vicious strain may be 

 modified, and even totally extinguished, by a favourable en- 

 vironment, for this virulent bacillus may be so attenuated by 

 cultivation in mild nutrient media as to become harmless even 

 to animals ordinarily the most susceptible, such as mice and 

 guinea-pigs. 



