cHAi'. v.] THE a4rV MUSCLE,-^. 14:) 



the rectus, and passes outwards to Le inserted between tlie fifth and 

 the :<ixth hindmost digitatious of the sorrutus magnus, just behind 

 the hinder end of the scalenus primus. 



External to the abdominal muscles the trunk is invested by an 

 aponeurosis called the superficial farcin. At its posterior part this 

 fascia is separable into two layers, the deeper of which adlieres to 

 Poupart's ligament, while the more superficial is (in the male) 

 prolonged into the scrotum — surrounding the structures which pass 

 from out the abdominal ring into that recei^taclc. 



Internal to the abdominal muscles, the abdomen is lined by a 

 membrane called the y^sc/r^ tmmrersaUs. It is pierced near its hinder 

 margin by an opening called the internal abdominal rincj, through 

 which the spermatic cord passes in the male. 



Lerator caiidce cxfcrnus. — This is the continuation backwards of 

 the longissimus dorsi, and arises from the lumbar and sacral trans- 

 verse processes, and is inserted by a succession of long, delicate 

 tendons into the metapophysial parts of the caudal vertebras suc- 

 cessively. This and the follomng muscle bend the tail upwards. 



The levator candid inicrnus. — This is the continuation backwards 

 of the semi-spinalis, and is a yet more medianly-placed dorsal muscle. 

 It is formed of a number of delicate, fleshy bellies and tendons, 

 which connect the dorsal and lateral regions of successive caudal 

 vertebra?. 



The puho-coccygeu>i is a thin, flat muscle which arises from inside 

 the pubis and goes to the ventral aspect of the third, fourth, and 

 fifth caudal vertebrte. 



The ilio-cocciKjeus passes from the inner side of the ilium to the 

 ventral surfaces of the fourth, fifth, sixth, and seventh caudal 

 vertebra}. 



The mcro-coceygeus arises (on each side) from the lateral part of 

 the ventral surface of the sacrum, and from the sides of the ventral 

 surface of the first eleven caudal vertebrco. It sends its tendons 

 forth back al<3ng the ventral surface and side of the tail to its 

 extremity. 



The infra-cocci/fjeus is situated in the mid-ventral line of the tail, 

 thus connecting together its successive vertebrae. 



The above four muscles bend the tail downwards. 



The ischio-cocci/fjeus is large and thick. It springs from the spine 

 and internal surface of the ischium, and is inserted into the whole 

 length of the transverse processes of the first four caudal vertebra). 



Inter-tran'^rersarii caudce are small slips connecting laterally the 

 successive caudal vertebra). It takes origin from the transverse 

 processes of the last sacral vertebra. 



This and the preceding muscle flex the tail laterally. 



The following muscles are found in the vicinity of the root of the 

 tail, and are some of them connected therewith : — 



Levator scroti. — This is a cutaneous muscle which arises in the 

 dorsum of the tail at about the fifth caudal vertebra, and becoming 

 connected with the -sp/iincfcr a)ii extcrnus expands upon the scrotum 



