ACID-FAST GROUP 309 



The disease in its various forms in man and animals has been 

 known since ancient times. Villemin, in 1865, showed that the 

 disease could be transferred from one animal to another by injec- 

 tion of the crushed nodules. He did not succeed in discovering the 

 specific organism, however. In 1884 Dr. Robert Koch presented 

 the results of his studies of the disease and described the organism 

 which he had proved to be its etiological factor. This work will 

 always stand as a model of scientific research in bacteriology 

 carried out under the most difficult circumstances. Staining 

 methods and culture-media were both devised before the organism 

 could be seen or grown. Koch succeeded in demonstrating its 

 presence in the characteristic lesions, in growing it upon artificial 

 media, and in reproducing the disease in animals by the inocula- 

 tion of pure cultures. It was assumed in the beginning that tuber- 

 culosis in all animals was caused by the same organism, but in 1896 

 Theobald Smith called attention to the fact that certain differ- 

 ences in cultural, morphological, and pathogenic characters could be 

 distinguished in the organisms isolated from human and bovine 

 tuberculosis. Koch, in 1901, declared the two organisms to be 

 distinct, and that the probability of human infection with bovine 

 tuberculosis was remote indeed. Since that time the subject has 

 been studied with varied results by many investigators. Prob- 

 ably more has been written on this one disease than any ten or 

 more other diseases. Journals devoted exclusively to tuberculosis 

 are issued. Many points even yet are not fully understood, but 

 the subject is upon a moderately sound basis at present. It seems 

 best to differentiate three varieties of the tubercle bacillus the 

 human, the bovine, and the avian. These possess many points 

 in common, and it is by no means certain that they cannot be 

 transformed the one into the other, but they may, in general, be 

 readily differentiated by specific morphological and physiological 

 characters. They will be discussed together. 



Distribution. Tuberculosis in man is known throughout the 

 civilized world. In the United States over 110,000 deaths occur 

 annually from this disease. It usually leads all other diseases in 

 total number of deaths produced. The disease in cattle is nearly 

 as widely distributed. It is found throughout Europe and America. 

 Isolated localities free from the disease, however, are known. 



