10 ANATOMY OF VERTEBRATES. 



The fleshy fibres of the transversalis abdominis, f, are closely 

 connected by dense cellular tissue with those of the internal 

 oblique ; they are arranged in finer fasciculi, and have, as usual, 

 a more transverse direction ; they terminate along the same line 

 as those of the internal oblique in an aponeurosis, g, which is 

 continued along the inner or central surface of the posterior rectus 

 to the median line. The lower boundary of the fleshy fibres of 

 the transversalis is parallel with the line extended transversely 

 between the anterior extremities of the ilia ; a fascia, less compact 

 than an aponeurosis, is continued downward from this margin, 

 and envelopes the cremaster and the constituents of the spermatic 

 chord, as they pass outward and forward beneath the lower edge 

 of the internal oblique. 



The pyramidalis, h, arises from the whole inner or mesial 

 margin of the marsupial bone, from which the fibres diverge, 

 the lower ones passing transversely across the interspace of the 

 bones, and meeting at a very fine raphe, or linea alba ; while those 

 fibres from the anterior ends of the marsupial bones gradually 

 exchange their transverse direction for one obliquely forward. 

 The breadth of each pyramidalis opposite the upper end of the 

 marsupial bone is more than an inch, the thickness of the muscle 

 one line. 



The rectus abdominis, i, comes off from the pubis along the 

 inner part of the strong ligamentous union of the broad base of 

 the marsupial bone, and expands as it ascends until it attains the 

 level of the ensiform cartilage, when it diminishes as it is inserted 

 into the sternal extremities of the ribs reaching to the manubrium 

 sterni and first rib in the Dasyures, as in the placental Carnivores. 

 The slight indications of tendinous intersections are confined to 

 the posterior or central superficies of the muscle. 



The cremaster, k, in the Phalanger and Opossum, is not a 

 fasciculus of fibres simply detached from the lower margin of the 

 internal oblique or transversalis, but arises by a narrow though 

 strong aponeurosis from the ilium, within and a little above the 

 lower boundary of the internal oblique, with the fibres of which 

 the course of the cremaster is not parallel ; it might be considered 

 as a part of the transversalis, but it is separated by the fascia 

 above mentioned from the carneous part of that muscle. Having 

 emerged from beneath the margin of the internal oblique, the 

 cremaster escapes by the large elliptic abdominal ring, I, bends 

 round the marsupial bone near its free extremity, and expands 

 upon the tunica vaginalis testis. In the female it has the same 

 origin, course, and size, but spreads over the mammary glands at 



