104 THE OSTEOLOGY AND MYOLOGY 



Well developed interspinals and intertransversals connect these processes as long as 

 the latter continue of normal size and shape. The first named muscles disappear first. 



The foregoing muscles all proceed over the back of the pelvis to the tail, above the 

 median lateral line of the latter. The remaining muscles constitute the tlexor series ; 

 these are best displayed by cutting open the symphysis pubis, and wrenching the sides of 

 the pelvis apart. Three arise from the innominate bone ; another (iiot here described 

 owing to an accident that destroyed my notes) arises from the face of the sacrum. 



Ischlo-coccygeus. — The most lateral of the flexor series. It arises fleshy from the edge 

 of the ascending ramus of the ischium, just below its junction with the ilium, and spreads 

 out to form a broad, fan-shaped muscle, that is inserted by separate fasciculi with the trans- 

 verse processes of the five or six upper caudals — beginning with the one next to that from 

 which the pyriformis arises. Its anterior border is in relation with the posterior border of 

 the latter muscle. Its action chiefly subserves the lateral movements of the tail, besides 

 serving as another attachment of this member of the body. 



Pitho-coccygeus. — This is the most anterior fasciculus of the general plane of muscle 

 that arises from the inner surface of the os innominatum. It takes distinct fleshy origin, 

 from the horizontal ramus of the pubes, opposite the articulation of the marsupial bone ; 

 and proceeds as a flat slip inward and backward, along the border of the ilio-coccygeus. It 

 has partial insertion, by aponeurosis, into the apex of the second V-shaped bone, but is 

 chiefly directly continuous with the following muscle : — 



Ilio-coccygeus. — Arises fleshy from the iliac bone not far from its middle, and represents 

 the posterior lateral part of the intra-pelvic muscles that pass to the tail. Narrowing some- 

 what from its original dimensions, it passes out of the pelvis alongside the preceding, with 

 which it is partially blended, and continues on the under surface of the tail, close to the 

 median line. These muscles, and the sacral ones, are of considerable size, and form the 

 bands of flexor tendons ali'eady noticed. 



Muscles of the Abdomen. 



The abdominal parietes are formed of five muscles, as in man, besides the quadratus lura- 

 horum, which was noticed in another connection. The pyramidalis, rudimentary or absent 

 in the human species, is here highly developed, as in the Monotremes proper ; the external 

 oblique, and rectus both have extensive thoracic prolongation. 



Obliquus externus. — This muscle is of great superficial extent. It arises by ten or 

 eleven thick fleshy fasciculi, from as many lower ribs, interdigitating with each of the three 

 serrati, but not with the latissimus dorsi. The external border of the latter overlies the 

 whole origin of the obliquus. The fleshy digitations begin at the middle of the second — 

 third ril), and upon successive ribs approach nearer the spine ; the last one arises at the 

 junction of the costal cartilage with its rib. From this point, the posterior margin of the 

 muscle descends straight to the tip of the ilium, and is bound down by a layer of common 

 intermuscular cellular tissue, hardly to be called an aponeurosis of the obliquus internus 

 (outer layer of lumbar fascia). From the tip of the ilium to the base of the marsupial 

 bone the lower border forms a well defined, stout "Poupart's ligament," continuous below 

 with the general fascia of the thigh ; beneath it, near its middle, the femoral vessels emerge 



