OF COLYMBUS TORQUATUS. 167 



Flexor carpi ulnaris. Of moderate size, fusiform shape, fleshy for nearly its whole extent ; 

 lying along the inner aspect of the ulna, its tendon inserted into the ulno-carpal bone, just 

 in the angle of the wrist joint. It is a direct flexor or adductor of the metacarpus. 



The phalangeal flexors and extensors do not seem to require special notice. 



Muscles of the Lower Extremities. 



As might be expected from the peculiar formation of the bony framework of the lower 

 extremities, and especially the shape of the pelvis, the muscles of this part of the bird 

 present many interesting features, as regards size, shape, position, line of fraction, etc. 

 From the great length, and extreme narrowness and flatness of the pelvis, the muscles 

 proceeding from it to the femur and tibia, or fibula, are of peculiar shape, and have fre- 

 quently unusual actions upon the bones they move. Thus, the line of traction of the 

 pubo-femoral muscles is such, that their action as femoral adductors is almost entirely lost, 

 and they have become rather extensors of the thigh. Other muscles again, ordinarily flex- 

 ors or extensors, seem to exert their chief action in producing the rotatory movements of 

 the leg and foot upon the thigh which in this genus are so perfect and extensive. From 

 the extreme tenuity of the sacrum, several muscles seem to take their origin from the 

 spine itself rather than from the pelvis. From these peculiarities of position and action, 

 I have found considerable difficulty in homologizing several of the muscles. I have gener- 

 ally noticed them in the order in which they successively appear in the prosecution of the 

 dissection. 



iSartorius. The first muscle given off to the lower extremities, arises apparently from 

 the spine of the dorsal vertebra about opposite the apex of the scapula ; passes down- 

 wards and outwards at an angle of 45°, overlying the latissimus dorsi, of a uniform width of 

 about three fourths of an inch, to be inserted, by a flattened tendon, into the inner aspect 

 of the projecting spine of the tibia, half an inch above the joint. It is fleshy throughout, ex- 

 cept just at its origin and insertion. 



It is a powerful internal rotator of the leg ; and to a less degree, an extensor. 



A broad, thin, fan-shaped muscle, the " rectus femoris," as homologized by most compara- 

 tive anatomists, arises from the median line of the sacrum for a distance of four inches, 

 commencing just below the origin of the preceding, with the lower border of which its 

 upper border is parallel and in contact ; lies superimposed upon the vasti, glutosi, and 

 crurams ; its fibres pass directly outw r ards, converging from this extensive origin to a narrow 

 flat tendon, which passes over the external condyle of the femur, to be inserted into the 

 head of the fibula. The muscle is tendinous for an inch or more at its insertion, and just 

 at its origin ; otherwise fleshy. 



It is a perfect external rotator of the tibia, and therefore the antagonist of the preceding. 

 From its insertion and the direction of its fibres it can have little or no effect as an ex- 

 tensor. Its shape is such that with its fellow of the opposite side it forms a perfect trape- 

 zium across the back of the pelvis. 



Biceps flexor cruris. A thin fan-shaped muscle, not unlike the preceding in shape, arises 

 from the pelvis near the median line, from opposite the acetabulum as far down as the 

 tuber ischii, being therefore partially overlapped by the preceding muscle. From this ex- 

 tensive origin of about three inches, the fibres proceed directly outwards, converging to a 

 flattened, then to a rounded, tendon. This tendon passes through a perfect fibrous loop, 



ME1IOLBS BOST. SOC. KAT. BIST. Vol. I. Pt. 2. 43 



