MUSCULAR SYSTEM OF AVES. HI 



The sterno-maxillaris ^ appears at first view to be the anterior 

 continuation of the preceding, but is sufficiently distinct to merit 

 a separate description and name. It arises lleshy from the 

 anterior part of the middle line of the sternum, passes directly 

 forward along the under or anterior part of the neck, expanding 

 as it proceeds, and gradually separates into two thin symmetrical 

 fasciculi, which are insensibly lost in the integument covering the 

 throat and the angle of the jaw. It adheres pretty closely to the 

 central surface of the constrictor colli, along which it passes to its 

 insertion. It retracts the fore-part of the skin of the neck, and 

 also the head. Each lateral portion acting alone would incline 

 the head to its own side : the whole muscle in action would bend 

 the neck ; but the movements of the head and neck are more 

 adequately and immediately provided for by the appropriate 

 deeper-seated muscles, and the immediate office of the present 

 muscle is obviously connected with the skin. Nevertheless, in so 

 far as this muscle acts upon the head, it produces the same move- 

 ments as the sterno-mcistoideus in Mammalia. 



The skin covering the dorsal aspect of the lower two-thirds of 

 the neck, besides being acted uj^on by the constrictor colli, is 

 braced doAvn by a thin stratum of oblique and somewhat scattered 

 fibres, dermo-transversalis^ which take their origins by fasciae 

 attached to the inferior transverse processes of the sixth to the 

 twelfth cervical vertebrae inclusive ; the fibres pass obliquely 

 upward and backward, and are inserted by a thin fascia into the 

 median line of the skin, covering the back of the neck. 



The representative of the platysma myoides^ is a thin trian- 

 gular layer of muscular fibres, taking their origin from the outer 

 side of the ramus of the jaw, and diverging as they descend to 

 spread over the throat, and meeting their fellows at a middle 

 raphe of insertion beneath the upper larynx and beginning of 

 the trachea, which they thus serve to compress and support. 



The dermo-spinalis arises by a thin fascia from the ends of the 

 spinous processes of the three anterior dorsal vertebrae. The 

 fibres slightly converge to be attached to the integument covering 

 the scapular region. 



The dermo-iliacus arises fleshy from the anterior margin of 

 the ilium. The fibres pass forward and slightly converge to be 

 inserted into the scapular integument. 



The dermo-costalis is a muscle resembling the preceding in 

 form. It arises fleshy, from the costal appendages of the seventh 



> XT.- vol. iii. pi. 34, e. - lb. pi. 34, fig. 1, (/. ' lb. pi. 31, e. 



