188 ALBERT KUNTZ 



cardiac, gastric, tracheal, oesophageal, pulmonary, and upper 

 intestinal plexuses are of vagus origin." 



The present series of observations on human embryos agree, 

 with regard to the genetic relationship of the pulmonary, the 

 cardiac, and the enteric plexuses to the vagus nerves, with the 

 earlier observations of the writer on embryos of other vertebrates. 

 In human embryos 5 mm. in length, in which the primordia of 

 the sympathetic trunks are present only in the thoracic and upper 

 abdominal regions, the vagus nerves may be traced distally 

 somewhat beyond the bifurcation of the trachea. Branches of 

 the vagi bearing small accumulations of cells of nervous origin 

 come into close proximity with the oesophageal wall. In em- 

 bryos of this stage as well as in embryos which are somewhat 

 farther advanced the vagus nerves have the appearance charac- 

 teristic of nerve trunks along w^hich cells of cerebrospinal origin 

 migrate peripherally. In favorable sections continuous lines of 

 cells of medullary origin may be observed extending into the 

 vagus rootlets (fig. 3, B), indicating an active migratory process. 

 In sagittal sections the ganglia on the vagus trunks appear as 

 large oval or elliptical cell-masses which are not sharply limited 

 distally. Furthermore, cells identical in appearance with those 

 present in the ganglionic masses are present in abundance in the 

 nerve trunks as far as the latter may be traced. These cells are 

 identical in appearance also with those which migrate peripher- 

 ally along the spinal nerves and the communicating rami. 



In embryos 6 mm. in length (nos. 241 and 676) branches of the 

 vagi may be traced distally as far as the cardiac region of the 

 stomach and for a short distance along its lesser curvature. 

 Wherever vagus fibers occur in these embryos they are accom- 

 panied by cells of nervous origin, many of which occur in small 

 aggregates. The primordia of the oesophageal plexuses may be 

 recognized at this stage. Vagus fibers accompanied by cells of 

 nervous origin may also be traced along the bronchi toward the 

 roots of the lungs. In embryos 7 to 9 mm. in length all of these 

 nervous complexuses have become better developed, the cell- 

 aggregates also have become more numerous and many of them 

 are larger. In sagittal sections of an embryo 9 mm. in length a 



