8 August, 1907.] 



Lameness in Horses. 



473 



when standing, very little weight was thrown on the limb and the hock was 

 flexed and " let down " three or four inches behind and below its fellow, 

 (see Fig. 75). When made to walk, at each step when attempting to 

 spring off that leg, the hock descended almost to the ground and it was 

 evident that the structures which support it were torn, and that the ex- 

 tensor muscles of the hock were powerless and evidently relaxed. There 

 was a fullness about the lower part of the quarter and symptoms of general 



Fig. 76. Rupture of Gastroc-nemeii. Preserved dissected limb showing the torn 

 muscles and the stripping of the periosteum from the front of the femur. 



distress were pronounced. The cause of the rupture was evidently either 

 a sudden slip forward of the limb with the hock partly bent, causing an 

 excessive strain on the gastroc-nemeii muscles (a very general occurrence 

 on the slippery wooden block pavement in the streets of Melbourne), or 

 a very severe effort of these muscles to extend, that is straighten, the hock 

 in an attempt to " lift " a heavy load — such an effort as more commonly 

 results in the springing of a " curb " or a sprain of the back tendons. 

 Figure 76 is a sketch of a dissection of the part of the limb involved 

 showing the torn muscles. 



