85 



hrm, the unvarying number contained in the neck of 

 man and (with the exception of the sloth) of quad- 

 rupeds. 



§ 86. The breast-bone is steadied at its upper 

 part by muscles which — replaced by equivalents 

 m quadrupeds — exist in their most simple manner 

 in man. We shall, therefore, since we do not aim 

 at discussing the minute differences of action 

 which make an alteration in these muscles neces- 

 sary, consider the type given in man as applicable 

 for reference, whenever we speak of these, or in- 

 deed of any of the muscles. 



In man these muscles, — from the upper end of 

 the breast-bone, called the sterno-cleido-mastoids, 

 or as we shall generally name them, the sterno- 

 mastoids, — are very prominent, and may be clearly 

 seen one on each side of the neck,"^* passing from 

 the top of the breast-bone upward, backward and 



* These muscles take their name in man from their various attach- 

 ments, viz., each on its side, to the breast-bone, the collar-bone, and the 

 mastoid protuberance of the skull, just behind the ear. In such ani- 

 mals as have no collar-bone the middle word of the name evidently 

 falls away. 



In the horse this muscle is replaced by two—" one, the ' sterno-max- 

 illarji,' is fixed to the anterior end of the sternum, and passes up the 

 front of the neck to be attached to the back part of the lower jawbone ; 

 the other, the levator humeri, is fixed to the front and upper part of tlie 

 round bone of the shoulder, and by a detached slip to the upper end of 

 the sternum, whence it passes up the front and side of the neck, to be 

 attached to the mastoid projection of the skull, giving off, on the way». 

 slips which are attached to the four or five upper neck vertebrae." 



