750 



A. SUBDA UAU AND V. H. JOHNSON ON THE NERVOUS 



in silver preparations, such as that shown in text-fig. 8, and it 

 seems probable that this path would agree with that of the 

 migrating nerve cells. 



Text-fio-ure 8. 



Transvorso section of chick (Ht-4i) from a Bielscliowslvj'^ prepnrntion, sliowing noi'vo 

 fibrils pursuing tho same course as the sympatlietic cell strand in fig. 7. 

 Tlie mcsoncliyme and otlior colls are much distorted, but somo of tiiosu nciir 

 tho dorso-latoriil angle of tho aorta show ovidenco of being Hynipalhetic in 

 character. 



Ao. Aorta. S.C. Spinal cord. V.B. Ventral root fibres. Sym.C. Sympa- 

 thetic cells. Ntc. Notochord, Ntr. Nerve fibres in the track of migrating 

 sympathetic cells. 



While it appears that many of these cells are sympathetic in 

 nature, the possibility must not be excluded that some of them 

 will develop into the sheath cells of Schwann. 



D. The Primary Sympatheiic Chain. 

 In their earliest stage the primordia of the sympathetic 

 chains consist of two paralli^l series of cell groups situated at the 

 dorso-lateral angles of the aorta. These are arranged meta- 

 merically and show a more advanced stage of development in the 

 anterior thoracic region. Ensuino; stages show their gradual 



