744 



A. Si;illlA KAU ANJ; r. U, .lOUNSON ON Tllli; NKIIVOUS 



aorta there are isolated cells with identically the same charac- 

 teristics as those of the crest, and clearly distinguishable from 

 the surrounding mesenchyme cells. The latter have much 

 smaller and spherical nuclei and are distinctly branched, their 

 processes being united so as to form a cell network. Their cyto- 

 plasm stains much lighter than that of the crest cells. The cells 

 proliferated from the ne\u-al crest axe not found in every section, 

 but ai'e most marked iia the inter-somitic regions, where later we 

 find the ganglia of the primary sympathetic cords. 



B. Iielciiions loith the Dorsal Root Ganglia. 



With the expansion of the neural crest to form the dorsal root 

 ganglia the procos of prolifeiation of sympitthetic cells increases, 

 and .as is shown in text-fig. 2 from Sparrow If) (= 42-hr. chick) 



Text-figure 2. 







Traiisvi-rse section of Sparrow embryo 15 (= 42-lir. cliick), showing' a succession of 

 ct'll.s (tij/.C.) migrating to tlie dorso-latoral angle of tlie aorta. 

 Jo. Aorta. Sy.C, Sympathetic cells. D.B.O. Dorsal root ganglia. 

 3Ii/. Myotome. Ntc Notochord. (Sp. 15, 3, 4, 15.) 



there is a succession of cells iipparently migrating to the dorso- 

 lateral angle of the aorta. These cells occur between the myotome, 

 now coiisidenibly developed, and the spinal cord. The colls still 



