178 FRED W. STEWART 



such as the v. Rath picro-acetic-osmic-platinic chloride. If we 

 take first the fiber picture alone, we find the superior laryngeal 

 nerve present as a large, well-developed strand. Passing caudad, 

 the vagus gives off fine branches to the developing esophagus, 

 these twigs forming a plexiform mass of fine, often single fila- 

 ments in the condensing mesenchyme of the future muscularis ; no 

 fibers can be traced into the region central to the muscularis. 

 The larger branches anastomose with similar fibers entering from 

 the inferior laryngeal nerve. At the junction of the inferior 

 laryngeal nerve with the vagus trunk there is an accumulation 

 of ganglion cells; their nature will be discussed later when they 

 may be examined to better advantage. Both vagi give off 

 esophageal branches below the level of the bifurcation of the 

 bronchi and send strands into the deeper portion of the cardiac 

 plexus anterior to the bifurcation of the bronchi and above that 

 of the Aa. pulmonales. Plexiform fibers connect the deeper 

 portion of the cardiac plexus with a more superficial portion, 

 with pulmonary branches, and with branches to the lower portion 

 of the vena innominata sinistra. This study does not concern 

 itself with the morphogenesis of the cardiac plexus save as refer- 

 ences to it are necessary in general description. The develop- 

 ment of the cardiac plexus deserves additional attention; even 

 after my rather superficial examination, it is quite evident to 

 me that the work of His, Jr. ('91), on the development of the 

 cardiac plexus of the chick, needs careful checking. In the 

 abdomen the vagus spreads out over the developing stomach 

 much as in the adult. Just before so doing the left vagus and 

 shortly afterward the right, communicate directly by large 

 branches with the coeliac plexus and indirectly by fine fibers 

 along the gastric branches of the coeliac axis. Due to additions 

 from other sources, above mentioned, it is quite impossible 

 henceforth to determine histologically how far caudad the vagus 

 extends. 



Other similarly prepared embryos of fifteen and three-quarter 

 days have furnished quite excellent impregnations of developing 

 neuroblasts in the gastric and intestinal plexuses. Neuroblasts 

 are found in large numbers in the condensing mesenchyme about 



