34 



ELEMENTAR Y ANA TOMY. 



[LESS. 



rarely the diaphragm may contain a sesamoid bone, as in 

 the Camel. There may be no tendinous centre, this being 

 absent in the Porpoise. 



In Reptiles (e.g. Iguana) a muscle, the retrahentes costarum, 

 (which appears to have no representa- 

 tive in man), arises by muscular fibres 

 from the sides of the bodies of the 

 trunk vertebras, and is inserted by 

 aponeurosis into the inside of the 

 seventh and eighth cervical ribs, and 

 into the seven following ribs. In 

 Tailed-Batrachians (e.g. Menopoma) 

 this muscle is very fleshy at its an- 

 terior end, and is carried forward 

 beneath the basis cranii. 



25. Of the MUSCLES OF THE IN- 

 FERIOR EXTREMITY. Thz psoas mag- 

 nus may be very much larger relatively 

 than in man (thus it is exceedingly 

 large in the Rabbit and Agouti), or it 

 may be (as in Birds and the common 

 Seal) entirely wanting. It has been 

 supposed that the great muscular mass 

 which in Cetaceans (e.g. the Porpoise) 

 and the Seals extends forward beneath 

 the trunk part of the spine from be- 

 neath its caudal part, is a psoas. 

 .'';W< ilaS This is not the case, however it is 



a sacro-coccygeus extraordinarily pro- 

 longed forwards. 



lliacits. This muscle may be want- 

 ing, as in the Whales and Seals ; or 

 relatively enormous, as in the Bats, 

 where it is inserted separately from 

 the psoas, and below the latter. The 

 iliacus (or else the psoas) may extend 

 its origin up to the last two dorsal 

 vertebras, as in Nycticebus. 



FlG. 305. SUBVERTEBRAL 



MUSCLES OF RIGHT SIDE 

 OF IGUANA. 



QL, quadratus lumborum ; 

 RC, retrahentes costarum. 



The psoas parvus may be altogether 

 anting, as in Cetaceans and Bir 



wanting, as in Cetaceans and Birds. 

 It may be as large as the psoas mag- 

 nus, as in the Pig, or ten times larger, as in the Kangaroo. 



A muscle may exist which extends from the coccygeal region 

 of the backbone to the femur, but which has no certain 



