THE MUSCLES OF THE UPPER EXTREMITY. 67 



the sternum, and following midway between tlie liml).s 

 of the furcula. Posteriorly, this linear division of the 

 pectoral integuments is carried well beyond the hinder 

 sternal margin. Next, make a similar median incision 

 upon the dorsal aspect of the body, meeting the circular 

 incision at the root of the neck, and carried posteriorly 

 as far back as the anterior border of the pelvis. Dissect 

 away the skin from the left side of the body, and from 

 the left upper extremity, leaving the right side covered, 

 in order to keep the muscles moist, and intact for com- 

 parison, if we find it necessary, with those of the side 

 we have under examination. 



Divide the dermal muscles as we come across them, 

 during our operation of removing the integuments, at 

 their middles, allowing the proximal portions to remain, 

 in order that their relations may be studied. 



In removing the integumental fold of the patagium 

 carefully study the mechanism of the tendons of the 

 patagii muscles, as well as the muscles themselves. We 

 also find in this fold other small muscular tendons, which 

 will hereafter be described. The relations of the pos- 

 terior patagial fold should also be carefully studied, as 

 well as the dermal muscles that lie within it. Great 

 care is necessary when you come to remove the skin 

 covering the pinion, as it is intimately attached to the 

 tissues overlying the muscles and tendons beneath it, in 

 several places, which are liable to be injured by the 

 scalpel if the removal is too hastily undertaken, or the 

 skin simply torn off". 



THE PECTORAL MUSCLES. 



49. The pectoralis major. 51. The pectoralis tertius. 



50. The pectoralis secundvis. 



This group of muscles is second to none in importance 

 as compared with any other in the entire muscular 



F 2 



