POULTRY DISEASES AND THEIR TREATMENT. 59 



relation to mammalian tuberculosis (Virchow's Arch. f. Path. 

 Anat. u. Phy.s., etc., Bd. 190, pp. 246-541, 1907). Their results 

 may be briefly stated as follows : Attempts to infect fowls 

 with riiammalian tuberculosis, like the earlier negative results 

 of other authors, have been fruitless. However, fowls are very 

 easily infected with avian tuberculosis by feeding them parts of 

 diseased birds. On the other hand, methods of infecting fowls 

 other than feeding are not always successful even with avian 

 tuberculosis. Other birds, especially cage birds, are very read- 

 ily infected in various ways. Parrots, in particular, are sus- 

 ceptible not only to avian tuberculosis but also to mammalian 

 and human tuberculosis. Also canary birds, sparrows, and va- 

 rious birds of prey were proven to be susceptible to both avian 

 and mammalian tuberculosis. In these respects such birds 

 differ materially from the domestic fowls. 



On the other hand their later researches have made it appar- 

 ent that a large number of mammals are susceptible to avian 

 tuberculosis. These include not only the small laboratory ani- 

 mals as rabbits, mice and guinea pigs, but also cattle, hogs, 

 horses, goats, and donkeys. Also avian tubercle bacilli have 

 been found in cases of human tuberculosis. On the basis of 

 such experiments and observations it appears that avian and 

 mammalian tuberculosis are not caused by different species of 

 bacteria but by different varieties of the same species. These 

 varieties have developed because the bacilli have grown for a 

 long period of time under different conditions. They are not 

 so different, however, but that they may grow in the environ- 

 ment best suited to the other one. 



It thus appears fJiat ivhilc foivls are not very likely to contract 

 tuberculosis from domestic animals or from man, yet fozvls that 

 have the diseases are a serious menace to the other animals 

 on tJie farm as zvell as to the poultryman. and his family. (Cf- 

 further on this point p. 64 below). 



Diagnosis. I'uberculosis 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. Morse (R. P. 

 J. Sept, 1910) says on this point: "There is a combination of 

 symptoms that might serve to arouse your suspicions; steadily 



