120 Diseases of Poultry 



culosis in cattle, yet usually such cattle do not react to the 

 ordinary tuberculin test. However, it has been found that in 

 a considerable number of cases of this disease the animals 

 will react if tested with a tubefculin made from the avian 

 bacillus. The majority of experimenters have reported 

 negative results in their attempts to infect cattle with the 

 avian orga,nism. The question is one which must await 

 further evidence before definite conclusions can be drawn. 



On the basis of such experiments and observation it 

 appears that the difference between avian and mammalian 

 tuberculosis has developed because the bacilli have grown 

 for a long time under different conditions. They are not so 

 different, however, but that each may grow in the environ- 

 ment best suited to the other. 



It thus appears that tvhile fowls are not very likely to contract 

 tuberculosis from domestic animals or from man, yet fowls that 

 have the diseases are a serious menace to the other animals on 

 the farm as well as to the poultryman and his family. (Cf . 

 further on this point p. 128 below.) 



Diagnosis. — Tuberculosis in mankind is so serious a 

 disease chiefly because it is so difficult to recognize it in its 

 earliest stages. The same is true with the disease in fowls. 

 There are positively no external symptoms by which the 

 disease can be recognized in fowls before the advanced stages. 

 Some of the outward symptoms that may serve to arouse 

 suspicion are : steadily advancing emaciation ; anaemia, 

 shown by pallor of comb, wattles and the skin about the 

 head ; general weakness ; lameness ; rufHing of the feathers, 

 and in many cases diarrhea. These combined with a bright 

 eye and a ravenous appetite are some of the symptoms most 

 frequently found. None of them is specific, however, and 

 final diagnosis must be based on other findings. Emaciation 

 is one of the best symptoms and in the last stages of the dis- 

 ease becomes very marked. Pernot cites the case of a Plym- 



