16 Practicum II. Muscles of the Fingers. 



most operations of the limb the act involves flexion, and extension merely 

 returns the parts to a condition in which the act may be repeated. 



41. Slit the skin through the middle of the wrist, the palm and 

 medius (middle finger). Dissect it up at both sides of the cut. Note 

 the thickness of the fibrous and fatty pad in the palm and on the finger, 

 constituting cushions, soft yet firm, warm yet not unwieldy. The spe- 

 cial, conical pad at the wrist is supported by the pisiform bone (PI. I). 



42. Cutoff the palmar skin and pad. Note the absence of any- 

 thing comparable with the mass of special short muscles constituting the 

 human "ball of the thumb." 



a. Also that, at the wrist, most of the muscles become continuous 

 with tendons which run in a channel between the pisiform bone and the 

 radius and are bound down by a fibrous band. 



b. Slit this band. Lift the muscle and tendon and note trie division 

 of the latter into four for the four fingers, and their reinforcement by 

 small muscles. 



c. Extend the hand to the utmost and spread the fingers as much as 

 possible. Hold the arm so that the hand cannot be flexed at the wrist. 

 Then pull upon the muscle and note that the fingers are both flexed and 

 drawn together. 



43. Extension of the fingers. Dissect the skin and fascia from the 

 dorsum. Several tendons will appear at the wrist. Disregarding those 

 which stop there, isolate one along the middle of the limb which divides 

 into branches, one for each finger. 



a. Trace one to the last phalanx of the medius. Cut between the 

 medius and the annularis and note the angles formed by the phalanges 

 with one another. 



b. Extend the medius and note that from the root of the claw there 

 extends to the distal end of the first phalanx an elastic fibrous band ; this, 

 without exertion upon the part of the animal, keeps the last phalanx 

 retracted and the claw thus "sheathed." 



