CHAPTER IV. 



DISEASES OF MUSCLES AND TENDONS. 



RUPTURE OF THE EXTERNAL ISCHIO-TIBIAL MUSCLE 

 (BICEPS FEMORIS). 



The biceps femoris muscle extends from the superior spinous process 

 of the sacrum to the region of the patella and the external surface of 

 the thigh. Above, it is inserted into the sacrum and the posterior 

 margin of the ischium, below into the supero- external surface of the tibia. 

 It completely covers the coxo-femoral articulation, and its passage over 

 the summit of the trochanter is lubricated by a serous bursa. The whole 

 of its anterior margin is connected with the fascia lata by an aponeurotic 

 expansion. From varying causes this aponeurotic layer may become 

 fissured ; during the backward and forward movements of the limb the 

 summit of the trochanter may enter the fissure and become fixed there 

 by the tension and resistance of neighbouring tissues. This accident 

 has been described as " displacement or rupture of the biceps femoris 

 muscle." 



According to Cruzel, fixation of the biceps femoris may occur, in very 

 thin animals, without rupture of the musculo-aponeurotic layer, the 

 process being then simply confined to stretching of the aponeurotic layer 

 over the summit of the trochanter. Under such circumstances the 

 musculo-aponeurotic layer presents a cup-like depression, into which the 

 summit of the trochanter fits, and thus effectually prevents movement of 

 the muscle. 



Whether the accident is due to an actual fissure, or only to stretching 

 of the aponeurosis, the symptoms are the same. 



Causes. The principal predisposing causes are thin condition and 

 malformation of the limbs (turning outward of the hind toes). 



The accident may occasionally be caused by a slip backw^ards, or by 

 extreme efforts in draught when ascending hills. 



Symptoms. Immediately the accident occurs the limb becomes fixed 

 in a position of maximal extension. The trochanter being caught, the 

 femur can no longer be flexed, and the lower joints are also fixed in 

 such a way that the limb can only be moved as a whole. The claws 



