294 PARTICULAR LAMENESSES. 



to this too soon after apparent cure, or it will most assuredly 

 cause a return of the lameness. Another fact should be remem- 

 bered, namely, that a high toe-piece on the shoe, by increasing 

 the resistance to the action of the muscles of the limb, may cause 

 this, as well as many other forms of lameness. 



SPRAIN AND ATROPHY OF THE CRURAL MUSCLES. 



That mass of muscular structure known as the crural muscles 

 is liable to sprain. It consists of the rectus femoris, arising from 

 the ilium ; the vastus externus and internus, arising from the 

 superior part of the femur ; and the crureus, arising from the 

 lower half of the femur. Their muscular structure is very 

 intimately blended, and they finally become inserted into the 

 superior surface of the patella. Their action is to extend and 

 elevate the thigh, and advance it under the body. 



The symptoms of injury or sprain of these muscles are inability 

 to extend the stifle and flex the hock, in fact to draw the limb 

 forward ; dragging of the toe when the patient moves ; when 

 standing still, the patella seems to have slipped down, and 

 there is knuckling over of the fetlock-joint, the whole limb 

 being posterior to its fellow. After a time the muscular struc- 

 tures become atrophied, individual muscles become prominent, 

 and a concavity presents itself between the anterior spine of the 

 ilium and the patella. 



Since the introduction of tramways, this form of injury has 

 become more common, owing to horses slipping on the rails. 

 This form of lameness requires long rest. 



STIFLE-JOINT LAMENESS 



Is of two kinds, namely, that within the joint proper, involv- 

 ing the condyles of the femur, the semi-lunar discs, and articular 

 head of the tibia (see Photo-lithograph, Plate II., Fig. 3) ; and 

 that in the patella articulation. The pathology of both forms 

 is alike — inflammation, ulceration of the articular cartilage and 

 of the semi-lunar discs, when the joint proper is involved, of the 

 deposition of the porcellaneous deposit, both in the cartilage and 

 Haversian canals of the bones, when caused by rheumatoid disease. 

 In stifle-joint lameness, the limb, when the animal stands, 



