2.  The organism so found must be grown outside of the body in what is termed pure cultures, that is, not associated with any other organisms, and for so long a time with constant transfers or new seedings that there can be no admixture of other products of the disease in the material in which it is grown.

3.  The disease must be produced by inoculating a susceptible animal with a small portion of such a culture, and the organism shown in relation to the lesions so produced.

It is worth while to devote some attention to the disease anthrax.  This occupies a unique position, in that it was the first of the infectious diseases to be scientifically investigated.  In this investigation one fact after another was discovered and confirmed; some of these facts seemed to give clearer conceptions of the disease, others served to make it more obscure; new questions arose with each extension of knowledge; in the course of the work new methods of investigation were discovered; the sides of the arch were slowly and painfully erected by the work of many men, and finally one man placed the keystone and anthrax was for a long time the best known of diseases.  Men whose reputation is now worldwide first became known by their work in this disease.  It was a favorable disease for investigation, being a disease primarily of cattle, but occasionally appearing in man, and the susceptibility of laboratory animals made possible experimental study.

Anthrax is a disease of domestic cattle affecting particularly bovine cattle, horses and sheep, swine more rarely.  The disease exists in practically all countries and has caused great economic losses.  There are no characteristic symptoms of the disease; the affected cattle have high fever, refuse to eat, their pulse and respiration are rapid, they become progressively weaker, unable to walk and finally fall.  The disease lasts a variable time; in the most acute cases animals may die in less than twenty-four hours, or the disease may last ten or fourteen days; recovery from the disease is rare and treatment has no effect.  It does not appear in the form of epidemics, but single cases appear frequently or rarely, and there is seemingly no extension from case to case, animals in adjoining stalls to the sick are not more prone to infection than others of the herd.  On examination after death the blood is dark and fluid, the spleen is greatly enlarged (one of the names of the disease “splenic fever” indicates the relation to the spleen) and there is often bloody fluid in the tissues.

Where the disease is prevalent there are numbers of human cases.  Only those become infected who come into close relations with cattle, the infection most commonly taking place from small wounds or scratches made in skinning dead cattle or in handling hides.  The wool of sheep who die of the disease finds its way into commerce, and those employed in handling the wool have a form of anthrax known as wool-sorters’ disease in which lesions are found in the lungs, the organisms being mingled with the wool dust and inspired.  In Boston occasional cases of anthrax appear in teamsters who are employed in handling and carrying hides.  The disease in man is not so fatal as in cattle, for it remains local for a time at the site of infection, and this local disease can be successfully treated.