504 DISEASE IN WILD MAMMALS AND BIRDS 
ology. Judging by the limited morbid processes produced 
by injecting avian bacilli into rabbits and guinea-pigs 
the reaction of the bird itself would not seem wholly 
responsible for the difference. The local tissue reaction 
in all avian lesions is mononuclear and fibrous, softening 
and pus being rare. It would seem from this and similar 
operations that the bird expresses its resistance to the 
bacteria by a fibrocellular reaction w^hich goes on to 
fibrosis mthout softening; perhaps this means also that 
their polynuclears are not sufficiently active, but the 
pathogenic power of the bacillus itself doubtless 
is individualistic. 
The character of the cheesy degeneration is likewise 
different from the mammalian. It seems like an abrupt 
hyaline necrosis of a large central mass and not the slower 
cell death seen in the other types of tubercle. At times 
the degenerated area, instead of having the yellowish 
color of caseation, will present what we have designated 
''gelatinous tuberculosis," the whole infiltrated area 
resembling boiled sago or tapioca. This seems to be a 
complete homogeneous coagulation or hyaline necrosis 
of the whole mass out to the delicate fibrous mantle sup- 
plied by the tissue in w^hich the tubercle lies. 
The organic distribution of tuberculous lesions has 
already received some attention and is to be discussed 
with the orders. There are, how^ever, some localities 
affected conspicuously in the bird. The skin lesions often 
attract attention during life. They occur around the eye, at 
wing joints, on the cresta stemi and on the legs. Parrots 
and jays have sho^vn nodular or diffuse gTO\vths around 
the eye, originating both in the lids and orbit, which on 
section have proved to be tuberculous. These seldom 
ulcerate, but those upon the skin of the breast and wings 
tend to have superficial erosions or deep ulcers. The latter 
lesions are more common upon pigeons but have been 
seen in Psittaci and Galli. Toucans and pigeons when 
