Warren Harmon Lewis 179 



the scapula. Its tendon of insertion is broad and thin and closely 

 applied to the capsular ligament. 



The three heads of the triceps muscle are easily distinguished. The 

 long and external heads are of about the same size. The anconeus 

 muscle is continuous with the triceps but arises from the external con- 

 dyle and passes to the side of the olecranon and adjoining surface of the 

 shaft of the ulna. 



The long 'head of the biceps muscle arises from the junction of the 

 eoracoid process and the head of the scapula and passes through the 

 bicipital groove. The two heads are inserted together into the con- 

 densed tissue swelling on the radius. 



The corncobracJtviUs muscle and short head of the biceps are inti- 

 mately connected for most of the length of the former. 



The brachialis muscle has spread out over more of the distal surface 

 of the humerus than in the preceding stage. 



The flexor muscles of the forearm are easier to distinguish than in 

 the preceding stage. 



The tendon of the palinaris longus is narrower in proportion than in 

 embryo XLIII. 



The tendon of the flexor carpi raclialis muscle can be traced farther 

 towards its insertion into the base of the second metacarpal than in 

 embryo XLIII. 



The muscle fibers of the flexor sublimis digitorum still run to the 

 carpus before the ^\ide tendon begins. This tendon soon splits into 

 four tendons which go to the four ulnar digits. These tendons are 

 better formed than in the preceding stage and split to surround the 

 tendons of the deep flexor. Their ends fuse with the thick perichon- 

 drium about the phalanges. 



The flexor carpi uhiaris muscle shows distinctly its two heads of 

 origin. It has a well-formed tendon of insertion. 



The deep flexor muscles can be separated into the flexor polUcis longus 

 and the flexor profundus digitormn muscles. The muscle fibers of the 

 profundus continue into the carpal region and end in a broad tendon 

 which divides at the base of the metacarpus into four well-formed 

 tendons. These fuse with the condensed tissue at the tips of the digits. 

 There is a slight split in each of these tendons near its end. The 

 tendon of the flexor longus pollieis behaves similarly. 



The pronator quadratns muscle is oval in cross section, and connects 

 the distal ends of the radius and ulna. 



The lumbricales are quite well developed and their fairly well-formed 

 tendons end in the perichondrium on the radial side of the digit. 

 14 



