AVIAN TUBERCULOSIS. — .ETIOLOGY. 527 



the amount of wasting may be estimated by palpation of the thorax 

 over the breast-bone ; the pectoral muscles fall away and the bone 

 projects prominently. At the same time other phenomena peculiar to 

 wasting may be noted : the comb loses its red colour, and the mucous 

 membranes become pale. The birds die in this condition ; towards the 

 end paralytic symptoms have several times been observed. 



Under these conditions diagnosis is difficult, but tuberculosis may be 

 suspected because it is the most frequent cause of wasting. Under 

 certain cicumstances, however, the observer may feel more certain 

 of the nature of the disease, viz. when external manifestations 

 occur, such as specific changes in the mucous membranes of the 

 head, in the subcutaneous connective tissue, and in the bones or 

 joints ; in the latter case considerable swellings may occur, especially 

 over the articulations of the wings and feet. 



Pathological Anatomy. — On post-mortem examination the intestine is 

 found affected in about half the number of cases. The peritoneum is 

 sometimes, and the spleen and liver are almost constantl}-, the seat of 

 new growths. 



Tuberculosis of the liver is indicated by the existence on its surface 

 and within its substance of tubercles varying in size between that of 

 fine dust and of a hazel-nut, but usually of about a pea. The super- 

 ficial nodules adhere to Glisson's capsule, beneath which they some- 

 times form slight projections. Whether superficial or deep-seated they 

 are whitish in colour when small, and greyish or yellow when of larger 

 size. Their shape is spherical, conical, or irregular ; and they may be 

 simple or confluent. They increase both the size and weight of the 

 liver in proportion to their extent and number, which latter is usually 

 considerable. 



The hepatic tissue between the tuberculous nodules is not always 

 unaffected ; on the post-mortem examination of two fowls affected 

 with " spontaneous " * tuberculosis we found in the right hepatic lobe 

 large haemorrhagic infiltrations ; in one the blood had traversed 

 Glisson's capsule and passed into the peritoneal cavity. 



In two pheasants affected with "spontaneous" tuberculosis, and in 

 four fowls which had been inoculated with avian tuberculosis, we found 

 fibrinous ascites ; in three cases this condition existed independently 

 of any change in the peritoneum, and appeared therefore to have 

 resulted from the hepatic lesions. On the other hand, six cases showed 

 peritoneal tuberculosis without ascites. 



After the liver the spleen is the organ most frequently invaded. 



* By the term "spontaneous" tuberculosis is here meant tuberculosis not produced by 

 experimental inoculation. — Jn'O. A. W. D. 



