110 ANATOMY OF VERTEBRATES, 



connected with the peculiar thickness of the integument, and 

 probably ^Yith the burrowing habits of this species, which thereby 

 possesses the power of shaking off the loose earth from its plum- 

 age, while busy in the act of excavating its chamber of retreat 

 and nidification. 



The whole of the neck is surrounded by a thin stratum of 

 muscular fibres, constrictor colli,^ directed for the most part 

 transversely, and extending from an attachment along the median 

 line of the skin at the back of the neck, to a parallel rajyhe on the 

 median line of the opposite side : this muscle is strongest at its 

 commencement or anterior part, where the fibres take their origin 

 in a broad fasciculus from the outer part of the occipital ridge ; 

 these run obliquely downward and forward on each side of the 

 neck, but are continued uninterruptedly with those arising from 

 the dorsal line of the skin above mentioned ; the direction of the 

 fibres insensibly changing from the oblique to the transverse. 

 The outer surface of this muscle is attached to the integument by 

 a thin and dense layer of cellular tissue, devoid of fat ; the under 

 surface is more loosely connected with the subjacent parts by a 

 more abundant and finer cellular tissue. 



Use, To brace the cervical integument, raise the neck feathers, 

 and in combination with the following muscle to shake these 

 parts. This muscle is well developed in the emeu, and acts when 

 the drum-like dilatation of the windpipe is sounded. 



The sterno-cervicalis ^ arises fleshy from the posterior incurved 

 angular process of the sternum, from the ensiform prolongation 

 and middle line of the outer and posterior surface of the same 

 bone. The fibres pass forward, and, diverging in gently curved 

 lines, ascend upon the sides of the broad base of the neck, and are 

 inserted by a thin but strong fascia into the median line of the 

 dorsal integument. This muscle is a line in thickness at its 

 origin, but becomes thinner as it expands ; the anterior part is 

 covered by the posterior fibres of the constrictor colli. 



Use, To retract the skin of the neck, and brace that portion 

 Avhich covers the base of the neck ; when these are the fixed 

 points, it will depress and protract the sternum, and thus aid in 

 inspiration. 



Ohs. In its position and the general course of the fibres, this 

 muscle is analogous to that which supports and assists in empty- 

 ing the crop in the common foAvl; but the oesophagus presents no 

 partial dilatation in the Apterjjx, 



' XI •. vol. iii. pis. 31, 34, or. - lh.T^\. ^\, b. 



