228 MUSCLES OF THE UPPER EXTREMITY. 



HAND. 

 Radial Region (Thenar). Ulnar Region (Hypothenar}. 



Abductor pollicis, Palmaris brevis, 



Flexor ossis raetacarpi (opponens), Abductor minimi digiti, 

 Flexor brevis pollicis, Flexor brevis minimi digiti, 



Adductor pollicis. Adductor minimi digiti. 



Palmar Region. 

 Lumbricales, 

 Interossei palmares, 

 Interossei dorsales, 



ANTERIOR THORACIC REGION. 



Pectoralis major, 

 Pectoralis minor, 

 Subclavius. 



Dissection. Make an incision along the line of the clavicle, from 

 the upper part of the sternum to the acromion process ; a second along 

 the lower border of the great pectoral muscle, from the lower end of 

 the sternum to the insertion of its tendon into the humerus ; and con- 

 nect the two by a third, carried longitudinally along the middle of the 

 sternum. The integument and superficial fascia are to be dissected to- 

 gether from off the fibres of the muscle, and always in the direction of 

 their course. For this purpose the dissector, if he have the right arm, 

 will commence with the lower angle of the flap ; if the left, with the 

 upper angle. He will thus expose the pectoralis major muscle in its 

 whole extent. 



The PECTORALIS MAJOR muscle arises from the sternal two-thirds 

 of the clavicle, from one half the breadth of the sternum its whole 

 length, from the cartilages of all the true ribs, excepting the first and 

 last, and from the aponeurosis of the external oblique muscle of the 

 abdomen. It is inserted by a broad tendon into the anterior bicipital 

 ridge of the humerus. 



That portion of the muscle which arises from the clavicle, is sepa- 

 rated from that connected with the sternum by a distinct cellular in- 

 terspace ; hence we speak of the clavicular portion and sternal portion 

 of the pectoralis major. The fibres from this very extensive origin 

 converge towards a narrow insertion, giving the muscle a radiated ap- 

 pearance. But there is a peculiarity about the formation of its tendon 

 which must be carefully noted. The whole of the lower border is 

 folded inwards upon the upper portion, so that the tendon is doubled 

 upon itself. Another peculiarity results from this arrangement: the 

 fibres of the upper portion of the muscle are inserted into the lower 

 part of the bicipital ridge ; and those of the lower portion, into the 

 upper part. 



