503 



4. M. teres major, 0-20 oz. 



These muscles are very remarkable, and are well shown in Pig. 35 

 {lat. d. and t. m.). The lat. dorsi takes its origin from the central portion 

 of the fourth rib (1| inch), and is inserted into the top and back of the 

 humerus, where it acts nearly 



as an opponent of the second Fig. 35, 



pectoral, as a depressor of the 

 arm. 



The teres major takes its 

 origin from the spinous pro- 

 cesses of the first and second 

 dorsal vertebra?, and from the 

 interspinous ligament, and is 

 inserted broadly (half an inch) 

 into the middle of the del- 

 toidal ridge, lying under the 

 deltoid itself. 



5, 6. M. pectoralis major et 

 minor, . . 0*27 oz. 



Arises from side of top of ster- 

 num and from upper sternal 

 ribs, and is inserted into the 

 pectoral ridge of the humerus, 

 and into the sheath covering 

 the biceps humeri. 



7. M. pectoralis secimdun, 

 0-37 oz. 



Takes its origin from the co- 

 racoid bone, from the top of 

 the sternum, and from the 

 coraco-clavicular membrane ; 

 and is inserted into the top of 

 the pectoral ridge. 



IN". B. — This muscle acts as a direct levator humeri, and its posterior 

 fibres are continuous with those of the deltoideus, which draws the hu- 

 merus backwards and upwards. 



8. M. deltoideus extemus, 0 3 6 oz. 



Takes its origin from the tip of the acromion, and from three-fourths 

 of an inch of the scapula behind it ; and is inserted halfway down the 

 arm, along the back of the deltoidal ridge. 



9. M. coracobrachialis, 0*16 oz. 



Arises from the posterior edge of the coracoid, and is inserted into the 

 triangular space lying inside the pectoral ridge on the head of the hu- 

 merus. 



10. M. triceps humeri (Fig. 35, tri) 



0-32 oz. 



