328 DADD'S VETERINARY MEDICINE AND SURGERY. 
THOROUGH-PIN. 
The seat of thorough-pin is between the popliteous (fig. 2) and 
the point of the hock, near where the tendon is severed, as shown 
in the accompanying engraving. The disease is called thorough- 
pin, simply because the fluid contained in the bursal sac can be 
squeezed from one side to the other. 
VIEW OF SOME OF THE DEEP-SEATED MUSCLES IN THE REGION OF THE HOCK ANb 8TIPFuk. 
Expianation.—l, Popliteous; 2, Flexor pedis accessorius; 3, Flexor metatarsi magnus; 
4, The tendon, common both to the flexor metatarsi and extensor pedis; 5, The groove 
‘no which the extensor plays. 
Symptoms.—The disease is similar to bog spavin and wind-galls; 
namely, enlargement of a synovial sac. It seldom if ever lames 
a horse, yet, when large, is apt to interfere with the free action of 
the joint. 
In former years it was customary to open thorough-pins by 
means of a lancet, in view of evacuating the fluid; but many fatal 
