THE MICROBES OF ANIMAL DISEASES. 



761 



TIIE MICROBES OF ANIMAL DISEASES.* 



By E. L. TEOUESSART. 



THE first of the virulent and contagious diseases in which the pres- 

 ence of a microbe was positively ascertained was anthrax, or 

 splenic fever, which attacks most of our horned animals, and espe- 

 cially cattle and sheep. 



As early as 1850, Davaine had observed the presence of minute 

 rods in the blood of animals which died of splenic fever ; but it was 

 only in 1863, after Pasteur's first researches into the part played by 

 microbes in fermentations, that Davaine suspected these rods of being 

 the actual cause of the disease. He inoculated healthy animals with 

 the tainted blood, and thus ascertained that even a very minute dose 

 would produce a fatal attack of the disease, and the rods, to which he 

 gave the name of Bacteridia, could always be discovered in enormous 

 numbers in the blood. 



The microbe so named by Davaine must from its characteristics be 



assigned to the genus Bacillus, and is now termed Bacillus anthracis. 



This disease, which affects men as well as animals, is characterized by 



general depression, by redness and congestion of the eyes, by short 







Fig. 1. Bacillus anthracis of splenic fever in dif- 

 ferent eta^es of development ; bacilli, spores, 

 and curled filaments (.much enlarged). 



Fig. 2 Bacillus anthracis, produced in Guinea- 

 pig by inoculation ; corpuscles of blood and 

 bacilli. 



and irregular respiration, and by the formation of abscesses, which 

 feature, in the case of the human subject, has procured for it the name 

 of malignant pustule. The disease is quickly terminated by death, 

 and an autopsy shows that the blood is black, that intestinal haemor- 

 rhage has occurred, and that the spleen is abnormally large, heavy, 

 and gorged with blood ; hence the name of splenic fever. The dis- 

 ease is generally inoculated by the bite of flies which have settled 

 upon carcasses and absorbed the bacteria, or by blood-poisoning 

 through some accidental scratch, and this is especially the case with 



* From " Microbes, Ferments, and Molds." By E. L. Troue?sart. Vol. lvi, " Inter- 

 national Scientific Series." New York : D. Appleton & Co. 1886. 



