HORSESHOEING. 35 



normal coBdition of the tendons is, therefore, absolutely 

 necessary to the horseshoer. Both flexor tendons are em- 

 braced and held in place by ligaments and fascia passing out 

 from the phalanges (Figs. 16, d' , and 24, e, f). The extensor 

 and flexor tendons essentially contribute to the strong union of 

 the phalangeal bones, and especially to the support and stability 

 of the fetlock- joint. The gliding of the tendons is made easy 

 by the secretion of a lubricating fluid, called ^synovia, from the 

 inner surface of the sheaths which surround them. In thin- 

 skinned well-bred horses with sound limbs one can not only dis- 

 tinctly feel the tendons through the skin, but can see their out- 

 line. When the tendons and hones are free from all inflammatory 

 thickenings, and the tendon sheaths are not visibly distended, we 

 say that the leg is " clean." 



Mucous Bursae and Tendon Sheaths. 



Accessory to the tendons, there are in the foot roundish, 

 membranous sacs (mucous bursas) and membranous tubes (ten- 

 don sheaths). Both contain a liquid resembling synovia (" joint- 

 w^ater"), which facilitates the gliding of the tendons. These 

 bursae and sheaths are often distended to form soft tumors, 

 known as hygromata (" mnd-puffs," "wind-galls"). 



(a) Mucous Bursae. — They lie beneath tendons at those 

 places where the tendons pass over bony prominences. 



1. The mucous bursa of the anterior extensor tendon of the 

 to© is about the size of a walnut, and lies between the tendon 

 and the capsular ligament of the fetlock-joint (Figs. 17, g, and 

 18, e). 



2. The mucous bursa of the extensor tendon of the long pas- 

 tern (lateral extensor) is somewhat smaller, and lies, likewise, 

 beneath the tendon, between it and the capsular ligament of the 

 fetlock-joint (Fig. 11, h). 



3. The mucous bursa of the navicular region lies between 

 tlie under surface (gliding surface) of the navicular bone and 

 the flexor pedis perforaris tendon (deep flexor). Its width 



