EPISKELETAL AND HTPOSKELETAL MUSCLES. 47 



transverse processes, and the sterno- and cleido-mastoidei 

 from the sternum and clavicle to the skull. 



The fibres of all these oblique muscles take a direction, 

 from parts which are dorsal and anterior, to others which 

 are ventral and posterior. 



The trunk muscles of the lower Amphibia exhibit ar- 

 rangements which are transitional between those observed 

 in Fishes and that which has been described in Man, and 

 which substantially obtains in all abranchiate Vertebrata. 



The muscles of the jaws and of the hyoidean apparatus 

 appeal- to be, in part, episkeletal, and, in part, hyposkeletal. 

 The mandible is depressed by a muscle, the digastric, arising 

 from the skull, and supplied by a branch of the seventh 

 nerve : it is raised by a muscular mass, which is separable 

 into masseter, temporal, and pterygoid muscles, according to 

 its connection with the maxillo-jugal bones, the sides of the 

 skull, or the palato-pteiygoid bones, and is supplied by the 

 fifth nerve. 



The proper facial muscles belong to the system of cuta- 

 neous muscles, and receive branches from the seventh nerve. 



The hyposkeletal system is formed, partly, of longi- 

 tudinal muscles which underlie the vertebral column; and 

 partly, of more or less oblique, or even transverse fibres, 

 which form the innermost muscular walls of the thorax and 

 of the al^domen. 



The former are the subcaudal intrinsic flexors of the tail ; 

 the pyriformis, psoas, and other muscles proceeding from the 

 inferior faces of the vertebrae to the hind limb ; the longus 

 colli, or intrinsic flexor of the anterior part of the vertebral 

 column; and the recti capitis antici, or flexors of the head 

 upon the vertebral column. The latter are the obliquus 

 intermcs of the abdomen, the fibres of which take a direction 

 crossing that of the external oblique muscle ; and the traiis- 

 versalis, which lies innermost of the abdominal niuscles, and 

 has its fibres transverse. In the thorax, the intercostales 

 interni continue the direction of the internal oblique, and 

 the triangularis sterni that of the transversalis. The dia- 

 phragm and the levator ani must also be enumerated among 



