180 FRED W. STEWART 



some evidence of an increased number of neuroblasts in the 

 developing intestinal coat at the point where additions from the 

 coeliac ganglion would seem probable. This may, however, be 

 purely physiological (Kappers, numerous papers on neurobio- 

 taxis). It will be noted likewise from the figure that there is 

 some slight indication of a splitting of the enteric plexus into 

 two concentric rings. This division of the plexus is not found 

 continuously; it is scarcely at all evident in the stomach wall, 

 largely so in the upper intestinal tract, and the condition grows 

 progressively less marked in the' more caudal loops of the intes- 

 tine. The doubling of the ring of neuroblasts apparently bears 

 no relation to possible additions from the coeliac. A morpho- 

 genetic factor might be suggested as responsible tor the late 

 separation into two plexuses — intermuscular and submucous — 

 in the stomach region; for example, the large increase in the 

 lumen of the digestive tube and consequently greatly increased 

 wall surface. 



Before discussing in further detail cell types and distribution, 

 it will be necessary to turn to still younger stages in order to 

 determine whether or not neuroblasts are present along the 

 gastro-intestinal tract before any confusion exists between vagus 

 branches and those from the coeliac plexus. Pyridine-silver 

 preparations of fourteen and one-half day embryos show develop- 

 ing neuroblasts in the gastric mesenchyme and in the mesenchyme 

 surrounding the intestine proper. Although nerve fibers are 

 beginning to grow outward along the coeliac axis and' superior 

 mesenteric artery, no connection between them and the fibers 

 of the vagus can be made out; they do not enter into gastric 

 or intestinal territory and no cellular contribution to the enteric 

 plexus is indicated. A similar condition has been noted by 

 Kuntz ('09) for pig embryos of from 6 to 7 mm. 



When this study was begun it was my belief that all migrant 

 cells — all neuroblasts which had wandered peripheralward from 

 the cerebrospinal ganglionic masses or neural tube (depending 

 on the interpretation assumed) — partook of the nature of sympa- 

 thetic elements, and I was rather at a loss to account for my 

 ability to quite early classify the neuroblasts into two distinct 



