THE COMMUNICABLE DISEASES 505 
pinioned, have on three occasions shown a tuberculous 
mass on the stump. 
Two parrots with hyperkeratosis of the beak and of 
the skin of the feet, have also had tuberculosis. These 
have been mentioned in literature as of tuberculous 
origin. One case well studied failed to show tubercle 
bacilli in the corns. In the absence of tubercle bacilli, one 
is inclined to think that this might be explained on the 
basis of a circulating toxin such as is assumed to be 
responsible for hypertrophic periosteitis. This latter 
condition has not been seen in birds. 
Still another type of occasional occurrence deserves 
mention. While most of the lesions in birds correspond 
to the description given in the preceding pages, 
some lesions fail to degenerate in the centre, retaining 
instead a solid homogeneous fleshy character of dull gray- 
yellow color. Upon section these have been found wholly 
cellular in construction. To distinguish them from the 
ordinary nodules they have been designated tuberculo- 
mata. Lesions of this kind may occur along the lymphatic 
paths, indeed seem more common in the lateral cervical 
and thoracic chain, and upon bones and nei'ves. When 
they are numerous the nodular caseous type is incon- 
spicuous. They suggest the bovine infection (Pearl dis- 
ease), but one attempt to prove this failed. We are of 
the opinion that this is the avian lymphatic form, as 
our examples correspond to the literary descriptions of 
cervical tuberculous lymphatics in birds. No especial 
variety of bird is more often affected by this process. 
Intestinal tuberculosis among the Aves may be said to 
assume three forms. The best known, indeed the form 
usually spoken of as representing the common picture, is 
that which produces varying sized nodules upon the 
serosa, sometimes associated with adhesions to neigh- 
boring intestines. Just how this type develops is not 
known. In some quarters it is believed to originate by 
the penetration of the tuberculous granulation tissue 
33 
