MUSCLES OF OUTSIDE OF THE SHOULDER 203 



bone, c, c, Plate in, figs. 2 and 3, and extending down 

 the fore part of the neck, is inserted into the middle 

 part of the lower bone of the shoulder, and thence con- 

 tinued down to the arm. The use of this muscle is to 

 bend the head ; or, the head and neck being fixed, to 

 elevate and bring forward the arm. When the horse is 

 running at full speed, with the head thrown forward, 

 this muscle is in powerful action. 



c, d. The serratus major, or great tooth-shaped muscle of the 

 shoulder, which constitutes a large proportion of the 

 lower part of the neck. It is deeply seated, arising from 

 the five last bones of the neck and the two first ribs. 

 Its lower portion springs from all the true ribs. The 

 whole of its fibres have a downward tendency, and are 

 inserted into the inner surface of the shoulder ; by 

 means of which the shoulder is attached to the chest, 

 and the weight of the body thereby supported. 



When the horse is in a standing position, this 

 muscle occasionally performs another important office. 

 The shoulders and legs, by means of the weight of 

 the body, are fixed and immovable ; consequently, 

 having no longer any power over the motion of the 

 limbs, it now exercises its power in enlarging the 

 cavity of the chest, and thus materially contributes 

 to give freedom to the action of the chest in 

 breathing. 



In treating of inflammation of the lungs, page 47, 

 we mentioned that horses labouring under this dis- 

 ease would stand night and day. The cause of this 

 is, that the breathing is laborious and painful, and 

 the animal in standing obtains the aid of this muscle 

 in giving ease to the respiration. Therefore, when 

 he does lie down, it is a pretty strong proof that the 

 violence of the disease has abated, and consequently 

 he no longer requires the assistance of this muscle. 



e,f. These parts represent portions of the trapezius muscle, 

 which is of a quadrangular form, and rises from the 



