Charles Eussell Bardeen and Warren Harmon Lewis 



27 



supply, but the femoral and obturator arteries also have appeared. The 

 blood is carried into the cardinal (iliac) vein partly by the femoral vein 

 and partly by the sciatic. The formed structures of the limb are sur- 

 rounded by a vascular mesenchyme. 



spiDal ganglion 



sciatic nerve, 

 Atid niusculatiir 



acetabulum 



femoral nerve, 

 and musculature 



/ '-.Os'^. 





^ 



abdominal 

 musculature 



Fig-. 25. Section through Embryo CIX. x 25 d. 



The conditions existing in the arm are considerably in advance of 

 those in the leg. The following description of the conditions in the arm 

 region can be followed from Figs. D and E, Plates IV and V. 



The lateral pre-muscle mass has become completely divided into sev- 

 eral groups. The tissue of these groups is now fibrillated. The first 

 division, the one which passes ventral to the brachial plexus, is seen 

 in Plate V. It constitutes the pectoral muscle mass, representing 



