OPERATION FOR PECTORAL FISTULA OF HORSES 



335 



the inflammatory process. The sternum, its cartilaginous 

 extremities, and sometimes the costal cartilages, are involved 

 in an inflammation that reflects upon the surroundings by- 

 causing the formation of an abundance of fibrous tissue, 

 perforated by one or a number of fistulous tracts that dis- 



PlG. 161— The Sternum of a Horse Affected with Pectoral Fistula. 



charge a limited amount of pus. Parts of the sternum ex- 

 foliate and may be removed through the tracts ; other parts 

 may become riddled with honeycombed compartments and 

 the adjacent cartilages may tumefy and finally undergo cal- 



FiG. 162— Sternum and Two Ribs of a Horse Affected with Chronic 

 Pectoral Fistula. 



careous degeneration. The course of the. process is decid- 

 edly chronic; there is no tendency towards spontaneous 

 cicatrization. On the contrary, the enlargement grows and 

 the osseous and cartilaginous invasion extends, until finally 



