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Show 290 MESSRS. B. C. A. WINDLE AND I'. 6. PARSONS ON [Nov. 3, Perineal aud Caudal Regions. Sphincter ani.-This muscle has the human attachments in male animals, but in females it is continuous with the sphincter vaginae, forming the sphincter cloacae. This is certainly the case in the Mare, the Sheep, the Chevrotain, and the Hyrax. Transversus perinei.-Thompson (XXXVI.) says that this muscle is absent in Ungulates; it is described, however, by Kinberg in the Chevrotain (X.) and by Chauveau in the Horse and Bull (II.) W e have seen it in the Sheep, but we agree with Thompson that it is not well marked. Bulbo-cavernosus.-As the bulb is a bifid structure in Ungulates, the two halves of the muscle are separated by a wide raphe and do not unite in the middle line. Ischio-cavernosus.-This is always well developed and rises from the inner side of the tuber ischii, it then turns forward, wrapping round the crus penis or clitoridis. Thompson gives a good illustration of it in the Camel (XXXVI.). The Compressor urethras surrounds the membranous portion of the urethra and consists, as in Man, of an upper and lower bundle ; it differs from the human muscle in not being definitely attached to the pelvic wall. Levator ani.-Thompson (XXXVI.) has shown that the levator ani of M a n is a compound muscle consisting of two modified tail-muscles- the ilio- and pubo-coccygeus supplied by the sacral plexus, and an ischio-anal muscle which is a derivative of the sphincter cloacae and, like that muscle, supplied by the pudic nerve. He points out that in the Ungulates only the ischio-anal muscle is present, and in this we can agree with him, though Gratiolet (III.) describes an ilio-coccygeus in the Hippopotamus and says that it is inserted into the anterior three caudal transverse processes. Ischio-coccygeus (Coccygeus).-This is well developed in the Artiodactyla, and rises from the pelvic surface of the ischial spine or the region where that structure would be, as well as from the sacro-sciatic ligament. It is inserted into the anterior caudal transverse processes. Lesbres (V.) points out that in the Equidae it is not well developed, and Chauveau (II.) agrees with this. Joly and Lavocat (XII.) deny its presence in the Giraffe, but Murie definitely found it in that animal. It is supplied by the sacral plexus. Sacro-coccygeus superior (Levator Cauda?; Extensor Cauda?). This rises from the sacral spines, and is inserted into the dorsal surfaces of the caudal vertebra? by a series of separate tendons. In those Ungulates in which the tail is well developed, a division into external and internal layers may be made out as in other mammals. Sacro-coccygeus lateralis is the continuation backwards of the semispinalis layer of the erector spina?. Sacro-coccygeus inferior (Depressor cauda?; Curvator coccygis). As Lesbres points out (V.), there are external and internal parts of this muscle, the latter being slightly developed and reaching only |
