132 DISEASE IN WILD MAMMALS AND BIRDS 
common in the lower animals. A diffuse fibrous thick- 
ening of a pearl gray glistening appearance, has occur- 
red in five monkeys harboring the Filaria gracilis in 
the peritoneum. 
Tuberculosis. 
In tuberculosis of this organ the capsule is almost 
invariably thickened over the nodules, but not over the 
whole organ and rarely in the diffuse variety. There is 
almost always, however, in this prolonged infectious dis- 
ease some reaction on the part of the spleen, particularly 
when several other viscera are involved. In such cases 
a low grade of general hyperplasia and fibrous tissue 
increase is found. This is especially true in the Primates 
and Carnivora in long continued pulmonary tuberculosis, 
and it is in this form that one does not often see tubercu- 
lous lesions proper in the spleen itself. Tuberculosis of 
the spleen is not very common in adult human beings and 
domesticated animals, while in the young it is seen in a 
fairh^ high percentage of cases. In the wild animals this 
organ seems much more susceptible to the settling of 
tubercle bacilli as vnll be attested by the facts to be cited, 
and yet there are some conspicuous exceptions to this 
statement. Just why certain groups, or orders should 
show splenic tuberculosis very frequently while others 
fail to do so is far from clear. 
The appearance of the lesion is fairly comparable 
throughout the animal kingdom, variations among the 
Aves being chiefly in the more frequent occurrence of 
the diffuse tuberculous splenitis. Miliary, caseous and 
conglomerate masses occur separately or together and 
without very distinct relation to other pathologi- 
cal involvements. 
The relative incidence of tuberculosis in the spleen is 
set forth in the section devoted to this infection, but may 
be mentioned here in a general way. The organ is about 
equally susceptible to the disease in mammals and birds 
