380 RESPIRATION. 



nuchae, and the spinous processes of the last cervical and all 

 the dorsal vertebrae, to be inserted into the upper border of 

 the spine of the scapula. Acting from its attachments to the 

 occiput, the ligamentum nuchae, the last cervical vertebra, 

 and perhaps one or two of the dorsal vertebrae, this muscle 

 may elevate the scapula and assist in inspiration. 



Pectoralis Minor and Inferior Portion of the Pectoralis 

 Major. These muscles act together to raise the ribs in diffi- 

 cult respiration. The pectoralis minor is the more efficient. 

 Tracing it from its attachment to the coracoid process of the 

 scapula, its fibres pass downwards and forwards to be attached 

 by three indigitations to the external surface and upper mar- 

 gins of the third, fourth, and fifth ribs, just posterior to the 

 cartilages. With the coracoid process as the fixed point, this 

 muscle is capable of powerfully assisting in the elevation of 

 the ribs. That portion of the pectoralis major which is at- 

 tached to the lower part of the sternum and costal cartilages 

 is capable of acting from its insertion into the bicipital 

 groove of the humerus, when the shoulders are fixed, in con- 

 cert with the pectoralis minor. In great dyspnoea, it is fre- 

 quently observed that the shoulders are braced, the pectorals 

 acting most vigorously to raise the walls of the chest. 



Serratus Magnus. This is a broad thin muscle covering a 

 great portion of the lateral walls of the thorax. Attached to the 

 inner margin of the posterior border of the scapula, its fibres 

 pass forwards and downwards, and are attached to the exter- 

 nal surface and upper borders of the eight superior ribs. 

 Acting from the scapula, this muscle is capable of assisting 

 the pectorals in raising the ribs, and becomes a powerful aux- 

 iliary in difficult inspiration. 



We have thus considered the functions of the principal 

 inspiratory muscles, without taking up those which have an 

 insignificant or undetermined action. In many animals the 

 n ares are considerably distended in inspiration; and in the 



