PLATE VIII. 



Figure H. Magnification aboiit 10 d. 



Drawing from a reconstruction of Embryo XXII; length, 20 mm.; age, 

 about 7 weeks (see also Figs. F, G and I). The dorsal musculature has 

 been removed. From the thoracic region all intrinsic muscles lateral to 

 the internal intercostal muscles have been removed down to the 8th rib. 

 The serratus anterior, however, has been left in position. The attachments 

 of the external oblique musculature are shown. The rest of the external 

 oblique muscle and a considerable portion of the internal oblique muscles 

 have been removed. The thoraco-abdominal nerves are exposed. The most 

 anterior nerve shown is the 7th cervical. The 7th cervical vertebra bears a 

 rib-like process. The cartilaginous portions of the vertebrae and ribs of the 

 first eight thoracic segments are represented. The ribs and vertebrae 

 distal to this point are shown covered with a dense embryonic connective 

 tissue. 



The skeletal portions of the arm are drawn without the condensed mes- 

 enchyme or perichondrium which surrounds all the cartilages. Portions 

 of the cartilages of the scapula, clavicle, humerus, ulnacarpus, metacarpus 

 and phalanges are shown. 



Most of the superficial muscles of the arm have been partially dissected 

 away. Most of the deltoid, the infraspinatus and teres minor, the teres 

 major and latissimus dorsi, the triceps and anconeus, the extensor digitor- 

 um communis and the extensor carpi ulnaris muscles have been dissected 

 away except for their attached ends which can be readily recognized. The 

 senatus anterior, supraspinatus brachialis, brachioradialis, extensor carpi 

 radialis longus et brevis, supinator brevis, abductor pollicis longus, exten- 

 sor pollicis brevis, extensor pollicis longus and extensor indicis muscles 

 are left intact. The intrinsic muscles of the hand as well as the insertions 

 there of the muscles of the forearm have been entirely cut away. 



The suprascapular, circumflex and radial nerves with their main 

 branches are shown. 



In the posterior limb portions of the rectus and sartorius muscles have 

 been removed so as to expose the chief branches of the femoral nerve; and 

 portions of the tensor vaginae femoris, gluteus medius and gluteus maximus 

 muscles, so as to expose the chief branches of the gluteal nerves. In the 

 leg a portion of the extensor digitorum communis muscle has been removed 

 so as to expose the extensor hallucis longus and the extensor digitorum 

 brevis muscles, and the distribution of the anterior tibial nerve. Portions 

 of the peroneal muscles have been removed so as to expose the distribution 

 of nerves to these muscles. 



In the anterior limb the cartilaginous portions of the skeleton are rep- 

 resented except at the joints, where some condensed tissue is pictured. 

 In the posterior limb is shown the condensed tissue which incloses the 

 cartilaginous portions of the skeleton. 



