The tubercle bacillus 487 



tuberculosis in New York amounted to 6,000, and that in Manhattan 

 alone there were constantly 20,000 persons suffering from the disease. 

 Cornet ' estimates that in 1894 the deaths in Germany from all other 

 infectious diseases amounted to 116,705, while those from tuberculosis 

 alone amounted to 123,904. Similar statistics might be chosen at will 

 from the health reports of any large city. While the disease is less 

 common in rural districts than in large towns, the difference is not so 

 striking as is generally supposed. 



In man, pulmonary infection is by far the commonest type. Be- 

 sides this, however, tuberculous processes may be found in the skin, the 

 bones, the joints, the organs of special sense, and the abdominal viscera 

 and peritoneum. No part of the human body is exempt from the danger 

 of infection. 



Infection in the human subject may take ^place by inhalation or 

 through the skin or the digestive apparatus. V. Behring ^ has within 

 recent years expressed the belief that a large percentage of all cases of 

 tuberculosis originate in childhood from infection by way of the intes- 

 tinal tract. He determined, as have others since his publication, that 

 tubercle bacilli may penetrate the intestinal mucosa without causing 

 lesions. Behring's contention has caused a great deal of discussion, 

 and the question he has raised is intimately bound up with the problem 

 of the virulence of bovine tubercle bacilli for himian beings, as he 

 assumes that the infection is due to the use of infected milk. 



The problem is plainly of the greatest importance hygienically, and 

 for this reason has been diligently investigated during the last few 

 years. The only reliable available method of approaching it has been 

 to isolate the tubercle bacilli from large series of diseased human beings 

 and determine for each case whether the guilty organism belonged to 

 the human or the bovine type. These types, as we shall see presently, 

 can be differentiated definitely by cultural characteristics and patho- 

 genicity, and it is not likely, at least in the light of our present knowledge, 

 that the type changes during the sojourn in the human body. Granted 

 this permanence of type, it is naturally of much value in revealing the 

 source of an infection, to determine whether or not a human being is 

 harboring a bacillus of the hxmian type or one of the bovine type. 



One of the most valuable contributions made to this problem during 

 the last three years is that of Park and Krumwiede.^ The accompanying 



^Cornet, "Die Tuberculose," Wien, 1899, p. 1. 



" V. Behring, Deut. med. Woch., 39, 1903 



' Park and Krumvjiede, Jour, of Med. Res., Oct., 1910. 



