THE MUSCLES OF THE LOWER EXTREMITY. 171 



which seems to be the homologue of the vastus externus 

 arises by a tendon on the outer aspect of the shaft of the 

 femur, at the base of the troehanter, and by fleshy fibres 

 adown the same side of that bone, nearly to the 

 condyle. 



The crurcpus has a bulk fully double the size of the 

 vastus externus ; it arises by a tendon from the anterior 

 and prominent rim of the troehanter above, and by 

 coarse, somewhat individualized bundles of muscular 

 fibres, down the antero-external aspect of the shaft 

 of the femur. These two muscles and the glutens 

 primus merge below with each other and into that 

 tendinous fascia which spreads over the front of the 

 knee-joint to be inserted into the cnemial crest of 

 the tibia, the fascia of the muscles at the outer side 

 of the leg, and has in it (in its usual position when 

 present, as it is here in the Eaven) the well-developed 

 patella. 1 



1 The gracilis muscle does not occur in the Raven, but as the 

 ambiens it received no little attention at the hands of Garrod and 

 Forbes, the former anatomist using it extensively in his classification 

 of birds. 



Mr. Forbes described the ambiens in the following words'! He 

 said : 



"This muscle, unlike the others to be subsequently mentioned, lies 

 on the lower or inner surface of the thigh. As generally developed, 

 it is a more or less slender fusiform muscle, which, arising from the 

 prcepubic spine or process of the pelvis, close in front of the acetabu- 

 lum, runs along the inner side of the thigh superficially, and then, 

 running slightly outwards, runs, as a thin tendon, in the fibrous 

 tissues covering the knee-joint (in some cases perforating the 

 patella) to the outer side of the leg, and terminates there by joining 

 one of the tendons of the superficial flexor of the toes, the flexor 

 perforatus digitorum. The course of this muscle will be made clear 

 by the accompanying representation of it, as seen in a Touraco 

 (Corythaix erythrolopha). In one or two cases (e.g. , CEdicnemus, 



