1894.] MYOLOGY or KODENTS. 279 



in which, moreover, the inner and outer halves of the muscle were 

 very distinct. 



Intercostals and Triangularis Stemi. — These muscles have nothing 

 remarkable in their attachments : the latter usually rises from the 

 posterior 4 or 5 pieces of the sternum. 



Tail-Muscles. 



The following muscles can be identified : — Extensor caudse, 

 externus and interims ; Abductor caudse, externus and internus ; 

 Flexor caudse, externus, internus, and profundus. 



AVith the following exceptions these muscles correspond to 

 Meckel's general description of the tail-muscles of mammals l : — 

 The abductor eaudas internus rises from one transverse process 

 and arches over to the next but one, passing dorsal to the inter- 

 mediate transverse process. 



The abductor caudae externus in Myopotamus does not rise from 

 the tuber ischii, its usual origin, but from the pelvic fascia by the 

 side of the lower part of the rectum. 



In Sphingurus the ischial origin of this muscle is very well 

 marked, as are also all the tail-muscles. In the flexor caudae 

 internus the most internal of the supernc'al tendons are inserted 

 first, the deeper tendons coming to the surface round the outer 

 side of these. In the flexor caudae externus the most external 

 tendons are first inserted, and the deeper ones reach the surface 

 round the inner side of these. 



In Castor a series of fleshy bellies rose from the articulations of 

 the chevron bones to the caudal vertebrae ; these soon became 

 tendinous and ran backwards and outwards to be lost in the fat 

 over the transverse process of the next vertebra but one. Each 

 tendon was perforated by the one behind it. 



Obliquvs Externus Abdominis 2 . — This muscle rises by fleshy 

 digitations from a large number of the posterior ribs, generally 

 about two-thirds of the total number, as well as from the lumbar 

 aponeurosis. The fibres pass downwards and backwards to be 

 inserted into the crest of the ilium, from which they pass across 

 as Poupart's ligament to the anterior part of the body of the pubes. 

 The next fibres are separated from these by a large triangular gap, 

 the external abdominal ring, and are inserted into the anterior 

 part of the body of the pubes. The fibres anterior to these pass 

 ventral to the rectus to reach the linea alba. In the anterior part 

 of the abdomen the fibres blend with those of the rectus, and in 

 some cases are continued forwards with that muscle to the first 

 rib. The intercolumnar fibres over the ring are well marked and 

 form a pouch for the testes. There is very little aponeurosis near 

 the linea alba, the most tendinous part being at Poupart's 

 ligament. 



1 Traite general d'Anatoinie compare e, p. 175. 



2 Owing to the fact that many of the animals I dissected had been eviscerated 

 before they came to me, my observations on the abdominal muscles are not so 

 complete as I could have wished. 



19* 



