8 Development of the Limbs, Body-wall and Back in Man 



of the arm lies opposite the 3d to 8th cervical and 1st thoracic spinal 

 ganglia. The upper arm still projects caudally. The forearm is more 

 flexed and projects ventrally; it is now quite well marked off from the 

 upper arm and hand. The digital swellings have increased and are now 

 visible on the margin as well as on the flattened surface of the hand. 

 The shoulder is more marked. The base of the arm is larger and 

 extends higher in the cervical region than in the younger stages. The 

 posterior limb shows a distinct differentiation of the foot. The knee- 

 bend may be distinguished. The hip region is not clearly marked 

 externally. 



Fiff. 11. 



Fig. 12. 

 X about 2^ d. 



Fig. 13. 



Embryo CLXXV. 

 Fig. 11 represents Embryo CLXXV; length, 13 mm.; age, about 5-| 

 weeks. Two photographs of this embryo are given in Plate I. The 

 various regions of the arm and the swellings of the digits are well 

 marked. The forearm has a more caudal projection than in Fig. 10, 

 In the posterior limb the various regions are more or less distinctly 

 indicated. In the foot digitation has begun. The body wall has ad- 

 vanced half-way across the surface of the liver. 



Enibryo CVI. 



Fig. 12 represents Embryo CVI; length, vertex-breach, 17 mm., neck- 

 breach, 15.5 mm.; age, about 5^ weeks. A photograph is reproduced on 

 Plate I. The limbs and body-wall are similar in development to those 

 of Embryo CLXXV, but the flexion at the elbow and knee is more 

 marked, and the body-wall lias advanced further across the abdomen. 



Embryo CLXVII. 

 Fig. 13 represents Embryo CLXVII; length vertex-breach 14.5 mm., 

 neck-breach 13.5 mm.; age, 5-|- weeks. A photograph is shown on 



