viii.] THE MUSCLES. 319 



The muscles belonging to man's palatal region are special 

 Mammalian muscles, and present in the class generally the 

 same disposition as in him. The pendulous palate becomes 

 in the Cetacea a muscular canal prolonging the posterior 

 nares to the elongated larynx which it embraces. 



19. The MUSCLES OF THE BACK of man present characters 

 as exceptional, when compared with those of Vertebrates 

 generally, as does his axial skeleton. The non-development 

 of a tail and the large size of the upper extremities are occa- 

 sions in him of muscular conditions which differ greatly from 

 those presented by many other forms. 



Thus the first and second layers may be entirely wanting, 

 and the other muscles may be represented (as in Menopoma 

 and Menobranchus) by one great mass, running from the head 

 to the end of the tail on each side of the vertebral neura- 

 pophyses ; and this again may be, as in Fishes (e.g. the Perch), 

 divided by a number of aponeuroses more or less at right 



-15 



FIG. 288. SUPERFICIAL MUSCLES OF THE PERCH. The fin-rays of all the fins are 

 cut short off. 



i, great lateral muscle, showing the numerous more or less vertical tendinous 

 intersections slightly inflected forwards and backwards ; 2, small superficial 

 muscles inserted into the fin-rays of the dorsal and ventral fins ; 4, slender 

 longitudinal muscle lunning (in the interval of the summits of the two great 

 lateral muscles) between the dorsal and caudal fins ; 5, similar muscle on the 

 ventral margin, which also appears between the anal and ventral fins ; 6, small 

 radiating muscles of the caudal fin ; 7, part of the great lateral muscle inserted 

 into the skull ; 8 and 9, elevators of the operculum ; 10, elevator of the palato- 

 quadrate arch ; it and 12, muscular mass which by its contraction closes th( 

 jaws; 13, superficial muscles of the pectoral fin; 14 and 15, muscles of the 

 ventral fin. 



angles to the backbone, so that the dorsal muscular mass 

 comes to consist not of segments extended in the line of the 

 skeletal axis, but of segments extending almost at right angles 

 to that axis. 



The muscles of the back may be much less developed, re- 

 latively, than in man, as is the case in Birds ; or they may be 

 all but absent, as in Chelonians. They may, on the contrary, 



