UPPER EXTREMITY AND THORAX, ANTERIOR. 301 



Nerve Supply. Ulnar, from first thoracic nerve. 



Action. To draw the skin toward the middle of the 

 palm. 



The palmar cutaneous nerves have already been dis- 

 sected ; their distribution is seen in removing the integu- 

 ment. The ulnar branch supplies the inner, the median 

 the middle portion of the skin of the palm. 



The Palmar Fascia. Fig. 65. 



This is the deep fascia covering the muscles (and vessels) 

 of the palm. The outer and inner thirds resemble the 

 deep fascia in other parts of the body in being thin and 

 forming a covering to the muscles. The middle third is 

 so strengthened by additional transverse and vertical fibres 

 that it becomes a very dense fascia. It is narrow above, 

 where it is attached to the annular ligament and receives 

 the fibres from the palmaris longus muscle, spreads out 

 fan-shaped below, where it divides into four fasciculi which 

 pass to the fibrous structures about the metacarpopha- 

 langeal articulations and lateral margins of the bases of 

 the first phalanges for their ultimate attachments. 



These fasciculi are bound together by cross fibres that 

 near the fingers exist as a separate band and are termed 

 the superficial transverse ligament of the palm. Between 

 these fasciculi the digital nerves and vessels are passing to 

 the fingers, and the lumbrical and interossei muscles at a 

 deeper level to their insertions. 



Each fasciculus just over the finger splits just before its 

 insertion to form a passageway for the tendons of the long 

 flexor muscles to pass on to the fingers. Distally each 

 fasciculus is continuous with the digital sheaths of the 

 flexor tendons. 



There is another fasciculus from the outer side of the 



