

3 



Fig. 1 Human embryo, 7 mm. in length, G17— 13— 1— SXl^^.* Transverse 

 section through lower thoracic region showing spinal nerve and sympathetic 

 trunk. To be compared with figure 13. A, aorta; CR, communicating ramus: 

 SN, spmal nerve; Srj, sympathetic trunk. 



Fig. 2 Human embryo, 6 mm. in length, 676-11-4-4. Transverse section 

 through upper abdominal region showing spinal nerve and sympathetic trunk 

 -4, aorta; CR, communicating ramus; PP, cells advancing into prevertebral 

 plexus; SN, spinal nerve; SY, sympathetic trunk. 



Fig. 3 A. Human embryo, 9 mm. in length, 721—12—3—4 and 5. Fiber- 

 bundles with accompanying cells in ventral root of spinal nerve B Human 

 embryo 11.5 mm. in length, 544-5-3-2. Vagus rootlets showing fibers with 

 accompanying migrant cells. ELM, external limiting membrane; X, the same 

 fiber bundle in successive sections 



* Numbers used in this manner indicate serial number of embryo, serial num- 

 ber of slide, row of sections on slide, number of section in row, and magnification. 



18:3 



