1882.] DR. GADOW ON THE ANATOMY OF PTEROCLKS. 317 



margin of the postacetabular ilium and from the lateral plaue of the 

 distal half of this bone. Its tendon passes through the tendinous 

 loop near the poplitea, and is inserted into the neck of the fibula. 

 Its nerves come from the ischiadic plexus. 



M. caudce ilio-jlexorms (m. seraitendinosus). See fig. 1. This 

 ribbon-shaped muscle arises from the lateral processes of some of the 

 first caudal vertebrae and from the outer plane of the spina ilio-cau- 

 dalis. The so-called accessory part of this muscle is well developed ; 

 it descends from the outer and lower surface of about the distal 

 third of the femur ; aud its fibres join those of the long or main part 

 nearly at right angles. The line of junction is indicated by an 

 oblique tendinous raphe. The two combined parts are inserted, 

 first into the neck of the tibia by a strong tendon ; secondly, a 

 small tendon, looking like the continuation of the raphe, descends 

 superficially to the back of the leg and joins the caput femorale 

 internum m. gastrocnemii. Nerve-supply, together with the next 

 muscle, from the ischiadic plexus. 



The m. ischio-fleocorius (m. semimembranosus) is feebly developed, 

 and loses its independence by becoming blended with the m. caudae 

 ilio-flexorius, which completely covers it externally. It arises from 

 a small part of the middle line of the lateral margin of the ischium. 



The m. caudce ilio-femoralis consists of two chief parts. The 

 most lateral one, or long head (long head of femoro-caudalis), is a 

 very narrow, slender, muscular ribbon, which arises from the proc. 

 lat. of the last caudal vertebrae, and is inserted by a narrow thin 

 tendon into the latero-posterior plane of the end of the proximal 

 third of the femur. Towards its insertion the fleshy part of this 

 long head is to a great extent blended with the more proximal or 

 greater part : the latter (accessory femoro-caudal) arises from part 

 of the membrane of the foramen oblongum, and from the outer 

 ])lane of the hindmost or distal part of the ischium, whilst only a 

 few fibres arise from the adjacent part of the ilium. The nerve 

 which supplies these two muscles comes from the ischiadic plexus, 

 and passes externally over the m. ischio-femoralis. I must mention 

 here a peculiar little muscular slip which I have not often observed 

 in birds. It arises (see fig. 1 ) as a small fleshy flat slip from the 

 outer aspect of that region where the pubis and ischium approach 

 each other ; it is then partly covered by the long head ; its thin 

 tendon unites with that of the long head. It was present also on 

 the other side, and was supplied by the same nerve-branch together 

 with the two large heads. The presence of this little muscular slip 

 is an instance of the great variation to which this group of the m. 

 caudae ilio-femoralis is subject. 



The m. ischio-femoralis (m. obturator externus) arises with 

 fleshy fibres from the dorsal, distal, and ventral margins ofthe foramen 

 oblongum ; its strong tendon is inserted into the outer plane of the 

 femur, just distad from the insertion of the m. obturator. It receives 

 its nerve from the ischadic plexus. 



The m. obturator arises from that part of the inner plane of the 

 ischium which bounds the foramen obturatum and also from the 



