382 



to the ganglia of the sympathetic trunks. The anlagen of some of 

 these plexuses he believes are composed of cells which grow out from 

 certain spinal nerves which, in the course of their peripheral growth, 

 come into close proximity with the visceral organs. 



The writer's observations on embryos of the pig lead him to con- 

 clude that the anlagen of the myenteric and submucous plexuses, the 

 pulmonary plexuses, and the cardiac plexus have their origin in 

 nervous elements which migrate from the vagus ganglia and the walls 

 of the hind-brain along the paths of the vagus nerves. 



/ 



& .^. >.■, 





vt. 



«^. 





fe 



bv. 



vt. 



Observations. 



1. Myenteric and submucous plexuses. 



In transverse sections of embryos of the pig 6 and 7 mm in length 



in the region of the oesophagus, the vagus trunks appear as large 



bundles of loosely aggregated fibers accompanied by numerous rounded 



or elongated cells. These cells which, as will be shown later, are 



jjjg obviously of medullary 



or ganglionic origin, 

 are easily distinguished 

 from the cells of the mes- 

 enchyme by the larger 

 size and the charac- 

 teristic chromatin struc- 

 ture of their nuclei. 

 Many of them appear 

 to become separated 

 from the nerve-trunks 

 and wander through the 

 tissues toward the oeso- 

 phagus until they have 

 completely surrounded 

 the latter. In a few 

 sections, short fibers are 

 seen to bend from the 

 vagus trunks toward the dorso-lateral angles of the oesophagus 

 (Fig.*^ 1 hv.). From the tips of these bundles of growing fibers, cells 

 pass in well defined paths toward the walls of the oesophagus and 

 spread out on its surface. It is probable that most of the cells which 

 become separated from the vagus nerves after their trunks have 

 become fibrous wander out along the fibers of these growing branches. 



Fig. 1. Transvei-se section through vagi and 

 oesophagus of 6 mm embryo of the pig. ^ 150. ac. 

 cells accompanying vagus fibers, bv. beginnings of 

 vagus branches, mc. cells migrating from vagus trunks 

 around oesophagus, nb. neuroblast, oe. oesophagus. 

 t. trachea, vt. vagus trunks. 



