Warren Harmon Lewis ITv 



The humerus is much hirger than in embryo XLIII, and has much 

 the adult shape, though of course it is thicker in proportion to its length. 

 It is composed of cartilage. There is a capsular and a coraco-humeral 

 ligament. No joint cavity exists between the scapula and humerus. 

 The tuberosities and condyles are fairly well formed in cartilage and 

 •condensed tissue. The bicipital groove is present. 



The ulna and radius are larger and longer than in the preceding stage 

 3ind are well formed in cartilage. The olecranon, coranoid and styloid 

 processes are partially formed in cartilage and condensed tissue. The 

 perichondrium about the ulna and radius is quite thick. The capsular 

 .and orbicular ligaments are present. No joint cavities exist and the 

 cartilages are separated by condensed tissue continuous with the peri- 

 •ciiondrium. 



Fig. 13. Cartilaginous skeleton of the arm of embrj-o XXII, lateral view. 

 X 12 diameters. 



All the bones of the carpus are represented by cartilage, and in about 

 their relative positions. The amount of condensed tissue matrix is 

 much less than in the preceding stage. The condensed tissue matrix 

 is continuous with the ulna and radius and the five metacarpals without 

 joint cavities. Indications of ligaments of the wrist are present. 



The five metacarpals are present in cartilage surrounded by thick 

 perichondrium. The first is the shortest. 



The first tAvo rows of phalanges are present in all the digits. They 

 are of cartilage surrounded by a very thick perichondrium, which is con- 

 tinuous with the condensed tissue between them and the metacarpals and 

 between the phalanges them.selves. It is also continuous with the 

 ■enlarged condensed tissue tip of each digit. There are thickenings for 

 the various ligaments connecting the metacarpals and phalanges and 

 the phalanges with each other. 



The Musculak System. — (Plate II, Fig. C.) The trapezius muscle 

 fibers extend from the occiput to the level of the sixth rib. There is a 



