Anthrax is more commonly known as _splenic fever_, _malignant pustule_, or _woolsorters’ disease_; in Germany as _Milzbrand_, and in France as _charbon_. It is an infectious disease of cattle, which has devastated many parts of Central Europe, and has been frequently met with on the Continent among men, though but rarely in the United States. All the domestic and nearly all the experimental animals are subject to it. Gronin has stated that in the district of Novgorod, in Russia, during four years more than 56,000 cattle and 528 men perished from anthrax. Poultry and dogs are not strictly immune, but possess a low susceptibility to the disease. It generally prevails in low districts and in marshy grounds. The disease is the result of the invasion of the _bacillus anthracis_, which is a relatively large-sized bacillus, varying in breadth from 1 to 1¹⁄₂ and in length from 5 to 20 microns. It is easily cultivated outside the body, and multiplies with great rapidity in the bodies of susceptible animals; it is the type of spore-bearing bacilli, and is so readily recognized and worked with that it is commonly used in laboratory investigations. The demonstration of its specificity we owe to Davaine, in 1873, although he had described it in 1850. [Illustration: PLATE IV FIG. 1 Anthrax Bacilli. Spore Formation. (Karg and Schmorl.) From an agar culture twenty-four hours old. About the margin of the photograph are a number of free spores, × 600. FIG. 2 Anthrax Pustule. Removed from Arm of Man. (Karg and Schmorl.) Marked edema of the skin, causing elevation and separation of the papillæ. In the edematous exudate a large number of anthrax bacilli and leukocytes. × 50.] _Anthrax bacilli_ may enter the body through the _respiratory organs_, through any _abraded surface_, and possibly even through the _alimentary canal_. They may also pass through the placenta and affect the fetus _in utero_. They are too large to pass through the walls of the capillaries of ordinary size; consequently they plug them and produce a mechanical stasis which is rapidly followed by gangrene. From the kidney structures and capillaries, however, they may escape, as bacilli are found in the urine in certain cases of anthrax. (See Plate IV.)