238 DE. J. MUEIE ON THE OEaANIZATION OF THE CAAING WHALE. 



The sphincter ani consists of a circlet of coarse, strong, tleshy fibres, the true external 

 spliincter ; but there are, besides, circular fibres more deeply placed around the gut, 

 which would represent a sphincter ani internus (vide fig. 48). 



The rectus abdominis, which I have already described, partly mingles with the 

 generative muscles, inasmuch as its posterior narrowed extremity and terminal tendon 

 enclasp the deeper fleshy structures of the vulva and winds round each innominate 

 bone, finally being inserted in the neighbourhood of the chevron bones. 



What I assume to be the counterpart of an ischio-coccygeus is a thick and strong 

 muscle which, with its fellow of the opposite moiety, constitutes a crescent-shaped 

 perineal mass. Each muscle arises by narrow but somewhat strong tendon from the 

 surface of the middle of the os innominatum. Passing backwards and inwards, its fleshy 

 fibres expand and are inserted into the perineal raphe, and join those of the levator 

 and sphincter ani. It is a retractor of the pelvic bone when the perineal attachment 

 is the fixed point ; reversely it may assist the levator ani. There is a likelihood also 

 that after pregnancy, when the mammary gland is enlarged, it may exert pressure on 

 that organ during lactation. 



The erector clitoridis, or ischio-cavernosus, is a large diagonally placed fleshy band of 

 muscle, of nearly equal breadth throughout. It lies partially beneath the last and 

 between it and the rectus abdominis, with the compressor mammae and gland to its 

 inner sides. Before the positions of the parts are disturbed this muscle has a more cur- 

 vilinear aspect than the deeper dissections (figs. 77, 78) warrant. It has an extensive 

 origin from the surface of the posterior moiety of the innominatum bone, at least 

 2 inches, as also from the fibro-cartilage and broad pelvic fascia. With a direction 

 forwards and inwards, it lies upon the sphincter vaginae, and is ultimately inserted into 

 the median line. In male Cetaceans the muscle corresponding to this is a very powerful 

 one, with a great pelvic attachment, and stretching on to the side of the root of the 

 penis. 



Alongside and mesially from the erector clitoridis is a somewhat fusiform, moderate- 

 sized, or, indeed, compared with the last, small-sized muscle. Its office I take to be 

 chiefly a compressor of the mammary gland, as such I name it ; for it constitutes a semi- 

 circle round and partially over that organ. Its attachment posteriorly is beneath the 

 ischio-coccygeus, from the strong perineal fascia in front of the rectum. From this the 

 muscle, sweeping outwards, forwards, and then inwards, or embracing the mammary 

 glands as a semilune, narrows anteriorly, and is fixed upon the strong fascia before and 

 partially at the side of the mammae'. 



Besides the two foregoing, two other muscles lie between them and the border of 

 the rectus abdominis. The first, in proximity to the erector clitoridis, is a short and 

 laterally compressed slip. Inwardly it is fastened to the median strong fascia of the 



' Geoff. St.-Hilaire, ' Annales,' 1834, p. 183, alludes to a muscular covering of the mammae, whicli, he thinks, 

 presses upon, the gland like the pouch of the Kangaroo. 



