TUBERCULOSIS IN THE HORSE. 229 



sanguinolent exudate. It is usually confined to the pleura or perito- 

 neum. Lesions of the pericardium, endocardium, and meninges are rare. 



In that form of tuberculosis known as abdominal the sublumbar 

 lymphatic glands are transformed into enormous bosselated swellings 

 covering the terminal portion of the aorta and origin of its branches, 

 and sometimes occupying the entire subvertebral groove from the 

 diaphragm to the pelvis. These swellings are superficially of uniform 

 consistence, but on section often show caseous or even calcified centres. 

 Their weight may even exceed 65 lbs. The mesenteric glands are more 

 or less hypertrophied and caseous, or partly calcified. The intestine 

 may exhibit ulcerations or tubercles. The liver and spleen are always 

 larger than normal, and may either be crowded with fine granules or 

 bosselated, covered with whitish swellings varying in size between a 

 hazel-nut and a child's head, uniformly dense, of the consistence of 

 sarcoma, or partially calcified, especially in the case of the spleen. The 

 common form of tuberculosis of the spleen can only be differentiated 

 from sarcoma and lymphadenoma by microscopical examination and 

 inoculation. In cases of old standing and extensive abdominal lesions 

 the lungs usually contained large numbers of granules and tubercles.* 



The statement of certain authors that calcification is not seen in 

 tuberculous lesions in the horse is incorrect. This change has really 

 been mentioned in a number of instances. I may add that athero- 

 matous degeneration and calcification of the walls of the common and 

 posterior aortae are fairly frequent in tuberculous horses. 



When infection has occurred by the respiratory passages lesions 

 maybe confined to thoracic organs like the lung, tracheo-bronchial and 

 mediastinal glands, pleura, and pericardium, but usually the abdominal 

 viscera, especially the mesenteric glands and spleen, are simultaneously 

 affected. When the bacilli have penetrated by the intestine the abdo- 

 minal organs, and particularly the mesenteric glands, liver, spleen, and 

 peritoneum — sometimes even the intestine — show older and usually 

 more extensive lesions than are met with in the thoracic cavity. Iden- 

 tification of the point of entry of the virus is not always so easy a 

 matter as one might be led to believe. It is principally based on the 

 size and age of the lesions in the abdominal and thoracic organs 

 respectively, and on the existence or absence of centres of degeneration. 

 When recent pulmonary tuberculosis is accompanied by extensive and 

 old-standing changes in the abdominal viscera, the virus has certainly 

 entered by the intestine ; but when the pulmonary lesions are of old 



'' Bacteriological and experimental investigations have led M. Nocard to conclude that 

 the pulmonary form of equine tuberculosis resembles human tuberculosis, and the abdominal 

 form avian tuberculosis. 



