DIAGNOSIS OF TUBERCULOSIS 461 



The last condition is relatively rare and may usually be detected 

 by physical examination. 



3. On account of the period of incubation and the fact that arrested 

 cases may sooner or later become active, all exposed animals should 

 be retested at intervals of six months to one year. 



4. That the tuberculin test should not be applied to any animal 

 having a temperature higher than normal. 



5. That an animal having given one distinct reaction to tuberculin 

 should thereafter be regarded as tuberculous. 



6. That the subcutaneous injection of tuberculin is the only method 

 of using tuberculin for the detection of tuberculosis in cattle, which 

 can be recommended at the present time. 



7. That tuberculin has no injurious effect upon healthy cattle." 

 Avian Tubercle Bacillus. Hens, pheasants and other birds are 



subject to a spontaneous disease which is anatomically very much 

 like tuberculosis of other warm-blooded animals. Koch 1 believed 

 that the organism of avian tuberculosis was identical with the bovine 

 tubercle bacillus, but later work has not confirmed this assertion. 

 It is believed at the present time that the bovine and avian tubercle 

 bacilli are distinct entities. 



The morphology of the avian tubercle bacillus and its staining 

 reactions are quite similar to those of the bovine organism, except 

 that pleiomorphism is more marked in the former, particularly when 

 it is grown at 40 to 42 C. It forms no spores and no capsules, is 

 non-motile and has no flagella. It grows more readily than either 

 the human or the bovine strains; the addition of glycerin to media, 

 while not essential, increases the luxuriance of the growth. On coagu- 

 lated blood serum or agar after six to ten days the organisms appear 

 as small white colonies with a waxy luster. A second transfer to arti- 

 ficial media results in a more luxuriant growth which spreads and 

 increases in luxuriance, eventually covering the whole medium. The 

 growth is moist and may become slimy, differing markedly in this 

 respect from the human and bovine types. The pellicle formed on 

 broth cultures is less friable and more tenacious than that characteris- 

 tic of the mammalian strains. The range of growth is from 35 to 45 

 degrees; 40 is the optimum temperature, but development is luxu- 

 riant at 37 C. An exposure of two hours at 65 C. usually fails to 

 kill avian tubercle bacilli but fifteen minutes at 70 to 72 C. is 

 fatal. The organisms are very resistant to drying, remaining alive 



1 Mitt. a. d. Kais. Ges. Amte, 1884, ii, 4. 



