336 CHAPTER 44. 



inelastic, fibrous structures, almost incapable of extension except under 

 strong persistent tension. 



The injury, which usually occurs, is inflammation caused by violent 

 usage. Occasionally some of the fibres of the tendon or ligament are 

 ruptured. Cases have indeed occurred, in which these structures have 

 been torn right across. In many cases, on the other hand, the tendon 

 itself is not injured ; but its synovial sheath only is sprained, or its blood- 

 vessels may be injured or ruptured. 



Among the public, any degree of injury from a slight increase of vas- 

 cularity in the vessels of the part up to an absolute tear of the fibres 

 right across goes by the common name of " sprain." Having made this 

 explanation, we shall adhere to the ordinary nomenclature, and use the 

 word " sprain " to express any injury short of absolute rupture. 



674. Structure of Tendons and Ligaments. 



Tendons .and Ligaments are mainly composed of white fibrous tissue; 

 but in ligaments the material is somewhat less closely put together than 

 in tendons, and it is also intermixed with yellow elastic tissue. See 

 Chapter 13, paragraph 234. 



A chief distinction between tendons and ligaments consists in their 

 attachments. Tendons may be defined as the passive instruments of 

 motion attaching muscles to bones. A tendon is inelastic or nearly so, 

 and i.s merely the " rope " acted on by muscles, by means of which one 

 bone is moved on another bone. Ligaments, on the other hand, are 

 usually attached to bones at each end, and hold them together. The 

 Metacarpal ligament, however, is inserted into the flexor perforans 

 tendon. 



675. Shortening of Tendons and Ligaments. 



Though tendons and ligaments are never permanently lengthened by 

 so-called sprains, yet they may nevertheless be, and frequently are, in 

 chronic cases after a length of time, shortened by such injuries. 



This result is produced partly by the deposit of material effused during 

 the process of inflammation, between the fibres which in consequence are 

 thickened and bowed out, and thereby practically shortened ; and partly 

 because the new material supplied for repair is not exactly the same as 

 the tendon or ligament, but a fibro-cellular tissue, which during the 

 healing process, has a peculiar tendency in itself to contract, and also to 

 draw together the edges of the wounded surfaces and structures. 



The standing over at the knees and fetlocks so often seen in horses, 

 that have done much work, arises from shortening, induced by frequent 

 sprains, and also from an altered condition of the articular ligaments of 

 the joints. 



676. Duties of Flexor Tendons. 



The Flexor tendons, though exceedingly powerful, being three times 

 as large as the extensors, are nevertheless very subject to sprain. Acted 



