1890. J PUBLIC DOCUMENT — No. 4. 329 



way. He fed three calves both with the hard and soft 

 varieties of a tubercle from a bovine lung ; and in a few 

 weeks marked symptoms of this aifection appeared, with loss 

 of appetite, rough, staring coats, occasional tits of coughing, 

 emaciation and diarrhoea. An examination of the dilierent 

 organs revealed characteristic lesions of the transmitted 

 malady ; and the fact that animals can contract this disease 

 through the agency of feed should give us new apprehensions 

 in the use of milk from infected cows, which may contain 

 the morbixl germs in question. The spread of this disease 

 by contaminated stalls has offered several opportunities 

 for its history and pathology. Dr. Grads' observations 

 at Leinhem paved the way for a series of microscopic 

 investigations, which culminated in this bacillus germ. He 

 chose a thriving young cow, well bred and healthy, and 

 placed her in an infected stall in which five animals had 

 previously died of tuberculosis. No change occurred to her 

 until after calving, Avhen a cough appeared, and gradually 

 increased in frequency, with emaciation and all the attendant 

 symptoms of this malady. The matter had become dried 

 on the boards of the manger, and was the only source by 

 which the germs of the disease could be conveyed to the 

 animal in question. 



In the hundreds of ex[)eriments by Koch, by inoculation 

 of the cultured bacilli into the abdomen or the eyes of the 

 guinea-pigs, rats, mice, rabbits, cats and dogs wdiich were 

 used, tubercle bacilli were found developing rapidly in a few 

 days or weeks, and in nearly all the organs of the body. 

 The results of these experiments ought to satisfy every can- 

 did mind that the old law, " like produces like," is true in 

 l)acterial pathology ; for all these animals, whether inoculated 

 in the subcutaneous tissues, peritoneal cavity, the aqueous 

 humor of the eye, or directly into the circulation, with 

 cultured bacilli, became tuberculous without a single excep- 

 tion, — not alone in a single place, but scattered throughout 

 all the organs of the body. All these facts led Koch to 

 proclaim, with that air of confidence which diligent labor and 

 research always inspires, that the bacillean germs occurring 

 in tuberculous substance were not merely the attendants of 

 the diseased process, but the cause of them ; and that bacilli 



