PLATE IX. 

 Figure I. Magnification about 12 d. 



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

 about 7 weeks (see also Figs. F, G and H). The thoracic, abdominal and 

 pelvic viscera have been removed. The attachment of the diaphragm to 

 the body-wall is shown. The intrinsic muscles and nerves of the thorax, 

 abdomen and pelvis are shown intact, and may be readily distinguished 

 by their relative positions. 



The ventral ends of the upper four ribs and the median end of the 

 clavicle are not shown. 



In the region of the shoulder and upper arm the deltoid, biceps, brachialis, 

 coracobrachialis and subscapular muscles are shown intact. The attached 

 ends of the pectoral muscles may be seen. In the forearm the following 

 muscles may be distinguished from above downwards: brachio-radialis, 

 pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum 

 sublimis and flexor carpi ulnaris. The brachial plexus is shown together 

 with the main nerves of the arm. Some of the interossei muscles are shown 

 in the hand. 



The brachial plexus arising- from the 5th to 8th cervical and 1st thoracic 

 nerves is seen. The relatively large size of the nerves and plexus is at once 

 noticed. The plexus itself forms a closely packed mass of fibers in which 

 it is just possible to distinguish the position of the three main cords from 

 which the principal nerves of the arm arise. The posterior cord is not 

 visible in this figure. The suprascapular, small nerve to the subclavious, 

 branch to the pectoral muscles, musculocutaneous, median, ulnar, and in- 

 ternal cutaneous nerves are seen arising from the plexus. 



In the region of the posterior limb the psoas muscle is shown cut away 

 over the lumbar plexus. The sartorius and vastus medius muscles may be 

 seen above the femur. In the region of distribution of the obturator nerve 

 the belly of the gracilis muscle has been removed so as to expose the 

 adductor muscles. The bellies of the semi-membranous and semi-tendinosus 

 muscles have been removed so as to expose the sciatic nerve, below which 

 The long head of the biceps may be seen. In the leg the gastroenemeus, 

 soleus, popliteus muscles, and the flexors of the toes may be distinguished. 

 The lumbo-sacral plexus arises from the 12th thoracic to the 3d sacral 

 spinal nerves. The inguinal nerve arises from in front of the first lumbar 

 nerve, the genito-crural from in front of the second, and the lateral 

 cutaneous from a point just above the region where the obturator and 

 femoral nerves are given off. From the lumbar plexus a large nerve bundle 

 passes into the psoas muscle. After passing Pouparts ligament the main 

 trunk of the femoral nerve may be seen below the sartorius muscle. The 

 long saphenus nerve may be traced to the ankle. The main branches of 

 the obturator nerve are shown. The pudic nerve may be seen passing out 

 between the great sacro-iliac ligament and the levator ani muscle, the pos- 

 terior cutaneous nerve is given ofE on the lateral side of sacro-iliac ligament. 

 The main branches of the tibial nerve in the leg and foot may be readily 

 followed. 



