422 DISEASES OF CATTLE. 



" pearly disease," on account of the peculiar appearance of the tu- 

 bercles. These begin as very minute grayish nodules, which give 

 the originally smooth, lustrous membrane a roughened appearance. 

 These minute tubercles enlarge, become confluent, and project above 

 the surface of the membrane as wartlike masses, attaining the size 

 of peas. In this stage their attachment to the membrane is by means 

 of delicate fibers. The attachment is loose, so that the tubercle hangs 

 b}' a short pedicle or neck and may be moved slightly to and fro. 

 Large masses are frequently formed by a coalescence of many tubercles 

 and the secondary formation of the same. These may be found on 

 the lungs, the ribs, and the diaphragm. These tubercles likewise 

 undergo degenerative changes. The center partly softens and partly 

 calcifies into a grayish mortarlike mass, and is gritty. Associated 

 with the formation of tubercles on the pleura, those glands situated 

 back of the center of the lungs between the two main lobes (posterior 

 mediastinal) become greatly enlarged and the center cheesy. (PI, 

 XXXVI.) They may compress the esophagus and interfere with 

 swallowing. The size attained by these tumors and new growths is 

 well illustrated by the fact that, taken together, they not infrequently 

 weigh from 60 to 80 pounds. The bronchial glands, which in the 

 healthy state are not so large as horse-chestnuts, have been found to 

 attain a weight of over 10 pounds. 



In the abdominal cavity tubercles may be found, both in the or- 

 gans and on the serous membranes covering them. They are situated 

 preferably on the omentum, or caul (see PI. XXXVII, PI. XXXVIII, 

 fig. 2), the diaphragm, and the walls of the abdomen. In the liver 

 large and small tubercular masses are occasionally encountered. 

 (See PI. XXXV.) The mesenteric glands (see PL XXXVIII, fig. 

 1) are occasionally enlarged and tuberculous; likewise the glands 

 near the liver. Tubercles may also develop in the spleen, the kid- 

 neys, the uterus and ovaries, and the testicles. 



Tubercular afi^ection of the intestines seems to be quite rare, 

 although ulcers of the large intestines have been observed. Nodules 

 may also form under the serous covering of the intestines. 



The brain and spinal cord are occasionally found tuberculous. Of 

 40 cases, Semmer found tuberculosis of the brain in 4. It is not 

 improbable that, owing to the infrequency of exposing the brain and 

 spinal cord, tuberculosis may have escaped the attention of patholo- 

 gists, and it jnay be that it is not so uncommon as is generally sup- 

 posed. The tubercles occur on the membranes of the brain as well as 

 in the substance of the brain itself. They project into the ventricles 

 as masses, varying in size from a pinhead to a hen's egg. They 

 finally lead to various inflammatory changes. Johne has observed 

 nimierous small tubercles on the membranes of the spinal cord. 



