TARSAL SHEATH— TENDINOUS THOROUGHPIN 143 



facilitate the gliding movements of the tendon through the tube we 

 have described, and it is the seat of the common surgical affection known 

 as tendinous thoroughpin. This is the name given to an over-distended 

 condition of the membrane. The enlargement may be recent, and due 

 to inflammation of the sheath as a result of injury, in which case the 

 swelling is hot, tense, and painful, but much more commonly it is a 

 dropsical condition, and the swelling is cold and not tender to the touch. 

 As the membrane becomes distended it bulges upwardly, and is particu- 

 larly evident on the inner aspect of the joint, where it will be found to 

 follow the course of the perforans tendon to the muscle from which it 

 arises. The swelling is therefore about two inches in front of the 

 tendo-Achilles. It is distinguished from a swelling of the capsule of the 

 true hock joint, which sometimes appears near this situation, by the tact 

 that the latter is more rounded and is placed immediately behind the 

 tendon of the flexor accessorius muscle. The enlargement under con- 

 sideration is elongated from above to below. Occasionally the swelling 

 forms a similar bulging on the outer aspect, the size of which may be 

 increased by applying pressure to that on the inner side. As a means of 

 distinction, also, it should be remembered that by pressing the enlarge- 

 ment above the hock it is frequently possible to cause a distension of the 

 sheath below the hock along the course of the perforans tendon. 



Occasionally, as a result of a kick or other injury, we have a cutaneous 

 wound and the sheath lacerated. Such cases should be dealt with 

 immediately, the usual treatment for wounds being adopted and the 

 strictest antiseptic precautions observed. 



In recent enlargements with acute inflammatory symptoms, cooling, 

 astringent applications should be utilised, followed by pressure bandages. 

 These latter should be applied most carefully, a layer of cotton-wool 

 being moulded over the swelling in order to obtain an even distribution 

 of the pressure. A marked diminution in size and frequently the 

 complete disappearance of the swelling may thus be brought about in 

 a very short time. Occasionally the swelling becomes chronic. The 



