64: LABORATORY EXERCISES. 



of the biceps with reference to the hu- 

 merus. 



B. The triceps muscle (an extensor muscle). 



1 . Clasp the back of the right upper arm with 



the left hand; forcibly straighten or ex- 

 tend the right forearm as much as you 

 can. Locate the belly of the triceps with 

 reference to the belly of the biceps, and 

 with reference to the humerus. 



2. By flexing and extending the forearm de- 



termine the position of the lower tendon 

 of the triceps. To which bone of the 

 forearm is it attached? 



3. (Dem.) Point out on the shoulder blade 



and humerus the attachment of the three 

 upper tendons. 



C. The flexor muscles of the fingers and of the thumb. 



1. Clasp the right forearm near the elbow; 



clench the hand quickly and forcibly. 

 Locate the belly of these flexor muscles 

 with reference to the bones of the fore- 

 arm. 



2. Press the forefinger and thumb strongly to- 



gether. What change is noticed in the 

 thick mass of muscle at the base of the 

 thumb? Along what bone does this 

 flexor muscle of the thumb lie? 



3. What would be the form of the hand if the 



flexor muscles of the fingers were located 

 in a position corresponding to the flexor 

 muscle of the thumb? What is gained 

 by placing these muscles in the forearm ? 



