TO BIED-ANATOMY AND CLASSIFICATION. 195 



muscles are the ambiens, the glutens primus, the semitendinosus, the acces- 

 sory semitendmosus, the femora-caudal, and the accessory femoro-caudal* . 



These will here be all considered seriatim ; they may all, it may be Ibis, 1881, 

 mentioned, be well seen in the common Fowl. P- 9< 



(1) The ambiens. 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 praepubic spine or process of the pelvis, close in front of the 

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

 turning 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 



Fig. 4. 



f-f- 



Thigh of Touraco (Corythaix erythrolopha) viewed from the inner side, to show the 

 ambiens muscle, arising from the praepubic spine of the pelvis (P), and running 

 along to blend with one of the tendons of origin of the flexor perforatus digitorum 

 (f.p.). F, femur; Pt, patella; 1.0, inner condyle of femur; T, tibia; b, biceps 

 (cut short) ; s, sartorius (also cut) ; e, e, extensor femoris ; sm, semimembranosus ; 

 add, adductores. 



N.B. The surrounding parts have been somewhat distorted from their natural positions 

 to show better the course of the ambiens. 



it, as seen in a Touraco (Corythaix erythrolopha). In one or two cases 

 (e. g. (Edicnemus, Stringops) it tends to become obsolete after reaching Ibis, 1881, 

 the knee, becoming lost in the capsule of the knee-joint. In all Passerine ^ 

 birds, and some others, it is always absent. 



* It is not my object in this paper to discuss the homology of the muscles here so 

 named with those of other Vertebrata. 



o2 



