400 Diseases of the (renital Organs 



The unsteadiness and inaccuracy of the gait, combined with 

 the frequent mounting of other cows, ultimately brings 

 about fractures of the pelvis in a large percentage of cases. 

 The fracture is usually through the shaft of the ilium. 



By studying Fig. 128a, it will be observed that the sacro- 

 sciatic ligament (1, 1', 3) is apparently designed to hold 

 passively in proximity the sacrum, ilium, and ischium. At 

 the same time it affords the chief base of support for the 

 long vastus and gluteal muscles. If, therefore, the ischial 

 tuberosity (Is) moves upward toward the sacrum, the liga- 

 ment loses its bone-like rigidity and the long vastus and 

 gluteal muscles drop inward, as shown in 2 and 3 of Fig. 

 129. The relaxation of the sacro-sciatic ligament deprives 

 the long vastus and gluteal muscles of their normal fixed 

 insertion and adds to the uncertainty of the step already 

 mentioned as resulting directly from the relaxation of the 

 ligaments. The anatomo-pathologic mechanism of the de- 

 formity is not .quite clear. The direction of the pelvis in re- 

 lation to the spinal axis is chiefly maintained by the sacro- 

 iliac ligaments, the psoas group of muscles, and the pre- 

 pubian tendon (linea alba). When the prepubian tendon 

 gives way, the ischial tuberosity moves upward and the iliac 

 tuberosity downward, but the sacrum moves in harmony 

 and the sacro-sciatic ligament retains its tone and tension ; 

 there is no sinking in. 



The basic cause of the ligamentous relaxation is yet more 

 difficult to determine. It has been compared with the pel- 

 vic relaxation upon the approach of parturition, but it is 

 utterly different. There appears to be some toxic substance 

 elaborated within the diseased ovaries which, acting upon 

 the central nervous system, causes these very remarkable 

 changes. 



In spite of good feeding, the cow frequently loses condi- 

 tion rapidly; the hair loses its lustre, and emaciation is very 

 marked. These changes are well portrayed in 2 and 3 of 

 Fig. 129. 



The disease occurs but rarely in heifers and is observed 

 chiefly in young cows. It attacks especially highly pedi- 



