234: PEIN0IPLE8 OF VETEEINAEY SUBGEBT 



The perforatus has a synovial sheath beginning at the 

 point where the perforatus tendon crosses the gastrocnemiiis 

 tendon and extending as far as the os calcis. When distended, 

 it appears as a swelling of variable size on either side of the 

 tendo achilles, just above the point of thfe os calcis. 



At the fetlock chronic distention of the sesamoidal sheath 

 enveloping the perf orans and perforatns is common. It is 

 much more frequent in the hind legs and more prone to 

 exhibit fibrous thickening in the wall of the sheath, represent- 

 ing, pathologically speaking, a chronic fibrous tendovaginitis, 

 or, as it is vulgarly called, a hardened wind gall. 



Which are the more common galls of the sheaths of the exten- 

 sor tendons ? 



Forelegs : The distended sheath of the extensor sufEraginis 

 starts three to four inches above the carpus on the outside of 

 the forearm and runs downward as far as the anterior face of 

 the carpus. 



The sheath of the extensor pedis, which is rarely seen dis- 

 tended, begins about six inches above the carpus, runs over 

 its anterior face to the upper portion of the metacarpus. This 

 tendon rests upon a mucous bursa of the metacarpus or meta-- 

 tarsus, occupying the anterior face just above the fetlock joint, 

 which may attain the size of an egg. 



The distended sheath of the extensor metacarpi magnus 

 occupies the middle of the anterior face of the carpus, but does 

 not go as far up or down as the one of the extensor pedis. 



The distended sheath of the extensor metacarpi obliquus 

 begins near the outside and about three inches above the car- 

 pus, running obliquely down and inward over the anterior 

 face of the carpus to the head of the inner small metacarpal 

 bone. 



