118 THE DISEASES OF DOMESTIC ANIMALS. 



variola acquires the disease ; the same is true even of syphilis, 

 gonorrhoea, diphtheria, and all the contagious diseases of man. It 

 is equally true with regard to pleuro-pneumonia, anthrax, rinderpest, 

 etc., of our animals, though the individual immunity to infection is 

 far less in some diseases than others. 



Again, syphilis can not be transmitted to our domestic animals ; 

 the glanders to the bovine family ; pleuro-pneumonia to man, or 

 most other animals, and so on of numerous other diseases ; while 

 rabies is the most generally infectious of all contagious diseases, 

 passing to nearly all warm-blooded animals. Foot-and-mouth disease 

 is, again, very general in its ability to infect the various species. 

 Man has a far greater receptivity to the contagious diseases of ani- 

 mals than they have to those of man. 



The carnivora possess a very slight degree of receptivity to an- 

 thrax, while birds and fowls are said not to possess any in a natu- 

 ral condition. Pasteur has endeavored to show, and has, in fact, ap- 

 parently experimentally proved, that it is the high temperature of 

 fowls, 42° C, which is the cause of this immunity to anthrax infec- 

 tion, formally the bacteria do not develop in their organisms, but, 

 when he cooled their bodies off artificially, they did develoj), and the 

 fowls died. 



I can not accept these conclusions, and think the immunity of 

 fowls must rest upon something else than their high temperatures, 

 for we know that a temperature of 42° C. is not at enmity with the 

 life of bacteria. 



At the time that the above-mentioned experiments of Pasteur 

 came out, I was myself busy in the experimental study of bacteria, 

 particularly bacillus anthrax. In the disease itself in cattle, sheep, 

 horses, and rabbits, the temperature frequently rises above 42° C. ; 

 then why do not the bacteria cease to develop, and the animals re- 

 cover ? 



I have frequently inoculated sheep that had a normal temperature 

 of 42° C, yet the bacteria developed and the animals died. Success- 

 ful reinoculations were also made from them. I have inoculated 

 horses suffering from influenza and pneumonia that would surely 

 have ultimately recovered, with a temperature of 42° C. or more, 

 yet the animals died from anthrax, and a plentiful development of 

 bacteria took place. 



The above condition is what is called "natural immunity." 



We have also what is known as " acquired immunity." 



A person who has once had the measles, whooping-cough, scar- 

 latina, variola, etc., seldom has the disease a second time. Excep- 



