122 THE OSTEOLOGY AND MYOLOGY 



Opponens minimi digiti. — Occupying the extreme ulnar margin of the hand, this small 

 muscle proceeds to the same insertion with the foregoing. It arises from the pisiform bone 

 and annular ligament. 



In the arrangement of these muscles of the lateral digits it is to be noticed, that the 

 thumb and little finger are each adducted and flexed by a broad plane of fibres proceeding 

 from the median line of the hand ; that each is abducted and extended by a more external 

 bulging mass of fibres. The flexores breves may be lost in the inner part of these last 

 named fibres ; and the opponentes be more or less blended with the outer part of the 

 same. 



Interossei. — The palmar are of large size, lie upon the metacarpals rather than between 

 them, and are much blended together, forming a fleshy mass that completely fills the con- 

 cavity of the palm. They seem rather to flex the fingers than to produce lateral move- 

 ments ; but when the fingers are fully extended, they may aid in spreading them apart. 

 There are four dorsal interossei perfectly distinct from each other, lying between the bones. 

 Each is pinnatiform, arises from contiguous sides of two metacarpals, and is inserted into 

 the radial side of the base of a finger. 



[Note. In the long interval between the preparation and publication of this Memoir, we have adopted for the muscles 

 that act upon the carpus and metacarpus the necessary change in nomenclature proposed by Wilder {these Memoirs, I, 

 1865, p. 32), by which the so-called "flexors" become extensors, and the so-called ''extensors" become _/?ejora. As the 

 change cannot now be readily made, the muscles are here presented under their usual names, with this explanation of an 

 apparent discrepancy between our determinations in the present instance, and those published for Man (N. Y. Medical 

 Record, July, 1810) and for the Ornithorhynchus (Pruc. Essex Inst., vi, 1871, p. 152), ( — see, however, the concluding Part 

 of this Memoir).] 



Muscles of the Posterior Extremity. 



The pelvic arch, unlike the scapular, being immovably connected with the body, is pri- 

 marily acted upon by but few muscles ; and those that pass from the body to the femur are 

 not many. Those that, though really attached in some way or another to the pelvis, act 

 not upon, but from it, are all considered in other connections, with the exception of the 

 psoas parvus, which is most conveniently described here : they are the perineal and abdom- 

 inal muscles, part of the vertebral series, and two special caudal muscles, the ilio- and 

 ischio-coccygeus. Two other caudal muscles, acting upon segments of the pelvic append- 

 age, most properly come under the present head. 



In consequence of extreme elongation and narrowness of the haunch bones, their over- 

 and under-lying muscles have rather unusual configuration. The six small muscles col- 

 lectively known in anthropotomy as "rotatores femoris," are all present and well developed. 

 There is a small muscle upon the hip joint not found in man. There is no tensor vaginae 

 femoris ; no crurscus or subcruroeus can be demonstrated. 



Psoas parvus. — (Fig. 31, c.) This muscle is well developed, being nearly as large as, 

 and much longer than, the psoas magnus. It arises fleshy from the bodies of all the lum- 

 bar vertebrjB, except the uppermost one, forms a stout conical belly, contracting opposite the 

 top of the ilium into a slender, flat tendon that is inserted into the horizontal ramus of the 

 pubes, nearly in front of the acetabulum, at a point just above and outside the articulation 

 of the marsupial bone. The tendon is dense and shining ; above, it spreads on the ventral 

 surface of the muscle; below, its edges and insertion are defined with remarkable sharpness. 



