PLATE V. 



Figure E. Magnification about 15 d. 



Drawing from a reconstruction of the regions of the arm, leg and body- 

 wall of Embryo CIX; length, 11 mm.; age, about 5 weeks. In the arm 

 region the cervico-brachial plexus, and the nerves and muscles of the arm 

 and hand are exposed (see text, page 27); in the region of the body-wall 

 the ribs, the spinal nerves, and the thoracic musculature (see text, page 

 26); ' and in the region of the leg the lumbo-sacral plexus and the main 

 nerves of the limb, the anlage of the limb musculature, the skeletal rudi- 

 ment and the blood-vessels. 



The five lumbar and the first three sacral nerves enter into the formation 

 of the lumbo-sacral plexus. The twelfth thoracic nerve, however, sends 

 a communicating branch to the ileo-hypogastric. From the first lumbar 

 nerve arise the ileo-hypogastric nerve and a communicating branch to the 

 lumbar plexus. From the lumbar plexus the femoral nerve may be seen 

 passing behind the pubic process of the hip-bone into the extensor muscle 

 mass. Just above the femoral nerve the genito-crural nerve arises from the 

 plexus. Between the pubic and ischial processes of the hip-bone the 

 obturator nerve passes forward into a mass of tissue which represents the 

 adductor musculature. Below the ischial process the sciatic nerve passes 

 into the limb, and from this the tibial nerve extends distally on the median 

 surface of the skeleton of the leg and terminates in the flexor musculature 

 of the foot. Along the course of the tibial nerve several muscle masses 

 may be distinguished. These represent the perineal, obturator internus 

 and quadratus femoris, ham-string and soleus-gastroenemus muscle masses. 

 Posterior to the tibial nerve the pudic nerve arises. The sciatic artery 

 passes in company with the tibial nerve, the obturator artery with the 

 obturator nerve, and the femoral with the femoral nerve. The border, 

 sciatic and femoral veins may be distinguished. 



lA portion of the interosseal musculature has been removed near the tips of the first 

 three ribs. 



