DISEASES AND INJURIES OF THE LEGS. 



191 



tlie parts should be kept clean for a few days, at the end of which it may 

 be necessary to reapply the caustic. 



If excision with the knife be preferred, the oj)erator must make his 

 incision in the perpendicular direction only, as a crucial incision leaves an 

 ugly blemish. Two incisions parallel to each other may be required in 

 very large tumors, and about an inch apart, in order to remove a portion 

 of the skin which, if left, would be an ugly blemish. 



THOROUGH-PINS. 



Definition. — Thorough-pin is the name given to a bursal enlargement 

 which occurs at the upper and back part of the hock beneath the great 

 extensor pedis tendon. The swelling appears sometimes on one side only, 

 but more frequently on both sides. (Fig. 96.) (See also Fig. 93.) 



Fig. 96. 

 Thoroiigh-pin. 



Etiology. — Overwork, sprain, faulty conformation, or chronic inflam- 

 mation of the joints may be set down as a usual cause; yet they sometimes 

 occur without any such violent exciting causes, and can then only be 

 attributed to either a special irritability of the synovial membrane, on 

 account of which it is excited to increased action on very slight provocation, 

 or to weakness of the coats of the blood-vessels of the membrane, through 

 which an undue effusion takes place. 



Chronic inflammation of the joints, which is often found as a result 

 of pneumonia, influenza, and sometimes of general debility, is another 

 common cause. 



