Page:Popular Science Monthly Volume 29.djvu/781

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HE first of the virulent and contagious diseases in which the presence of a microbe was positively ascertained was anthrax, or splenic fever, which attacks most of our horned animals, and especially 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



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 hæmorrhage has occurred, and that the spleen is abnormally large, heavy, and gorged with blood; hence the name of splenic fever. The disease 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