130 Lectures on Bacteria. [§ xii. 



nently infected. If no herds of cattle visit them, small animals, 

 the rodents especially, which are so susceptible of the disease, 

 may ensure the introduction and conservation of the Bacilli. 

 But these circumstances are, as was said, not directly necessary 

 for the existence of the Bacillus and of the risk of anthrax, not- 

 withstanding the importance which has been attributed to some 

 of the conditions connected with them. 



To complete this review of the subject we may remark in 

 conclusion, that the Bacillus and its effects appear to be trans- 

 ferable as might be expected from one living animal to another, 

 and the disease is propagated by this transmission. This infec- 

 tion belongs of course to the category above distinguished, of 

 anthrax as produced by inoculation or by a wound. It can 

 only be brought about by means of vegetating rods, because 

 these alone are present in the living animal, and the rods, as we 

 saw, must be conveyed directly into the blood of the living 

 animal, to be capable of further development. And now the 

 conditions of infection have been sufficiently indicated for 

 our purpose. A possibly exaggerated importance has been 

 ascribed to stinging flies and gnats as agents of infection, 

 since these insects, when they have sucked blood from an 

 animal which contains Bacilli and then puncture a healthy 

 animal for the same purpose, may easily effect a true inoculation 

 of the disease. 



The Bacillus of anthrax in the character of a parasite pro- 

 duces in the animals and in the cases which have been described 

 injurious effects, which may be provisionally compared to those 

 of a poison, and may therefore be termed poisonous and 

 virulent. 



This virulence may be gradually attenuated till it ceases to be 

 dangerous even in the case of that most susceptible of all the 

 animals experimented on, the domestic mouse. Pasteur has 

 shown that this takes place when the Bacillus is cultivated in a 

 neutral nutrient solution, meat-broth, especially chicken-broth 

 with a plentiful supply of oxygen at a temperature of 42-43° C. 



