92 



Basic Structure of Vertebrates 



EPAXIALT1 



— — 



TRICEPS-AMCONQJS 

 . BICEP: 



A NECTURUS 



im®r> 



DEPRESSOR MANDIBU1>E 

 SPHINCTER COU.1 



^^—J^d/Y^ I TRAPEZIUS '« 



TRANSVERSOSPINAL!! 



JGISSIMUS 

 LEOCOSTALIS 



IWOBUUB 



Fig. 91. Superficial lateral trunk-muscles in an amphibian, a reptile, and a mam- 

 mal. (A) Necturus. (B) Sphenodon. (C) Felis. The metamerism of the lateral trunk- 

 muscles, which is such a striking feature of the lower vertebrates, is retained in 

 urodeles and reptiles, but is much reduced in adult mammals. (Courtesy, Neal and 

 Band: "Chordate Anatomy," Philadelphia, The Blakiston Company.) 



some possible exceptions in the region of the head and neck, and in the 

 appendages) is at first definitely and completely segmented. In adults 

 those muscles which lack obvious segmentation are, nevertheless, built 

 up of segmented material. 



Special Groups of Muscles 



appendicular muscles 



The appendages grow out from the trunk. Their muscles are de- 

 rived from mesoderm of the trunk. In sharks the muscles of the pec- 



