388 



In a recent paper ('09) the writer has described the migration of 

 nervous elements from the neural tube and spinal ganglia along the 

 spinal nerves and communicating rami into the anlagen of the ganglia 

 of the sympathetic trunks. The large majority of these elements are 

 to be regarded as the "indifferent cells" of Schaper. Among them, 

 however, cells occasionally are found which answer to the description 

 of the "neuroblasts" of Schaper. These I have characterized as pyri- 

 form ^) cells. This, however, is inadequate since, although the cytoplasm 

 is usually drawn out to a point at one side neuroblasts do not ne- 

 cessarily assume a pyriform outline while that form may be approached 

 by indifferent cells. In order to avoid any confusion on this point 

 figures of several neuroblasts located in the spinal nerves and com- 

 municating rami, drawn with the aid of the camera lucida, have been 

 introduced in Fig. 4 a, h, c. It is obvious that not only the neuro- 

 blasts which havie already undergone differentiation, but also many of 

 the indifferent cells which enter the anlagen of the ganglia of the 

 sympathetic trunks give rise to sympathetic neurones. 



It is not the writer's purpose to discuss the relative importance of 

 indifferent cells and neuroblasts in the development of the sympathetic 

 plexuses considered in this paper. The important fact is that cells 

 which are endowed with the capacity to develop into neurones migrate 

 from the ganglia of the vagus nerves and the walls of the hind-brain 

 into the anlagen of these plexuses. Many of the indifferent cells 

 undergo division by mitosis along the course of the vagus nerves. 

 We, therefore, are not driven to the conclusion that all the cells 

 which enter into the formation of these plexuses (before any can be 

 supplied from the ganglia of the sympathetic trunks) actually migrate 

 from the vagus ganglia and the walls of the hind-brain. It certainly 

 is true that many are supplied by the division of indifferent cells as 

 they migrate along the vagus nerves. There need be no difficulty, 

 therefore, in concluding that the vagus ganglia and the walls of the 

 hind-brain constitute a source which is sufficient to account for all the 

 cells which take part in the early development of the myenteric and 

 submucous plexuses, the pulmonary plexuses, and the cardiac plexus. 

 We may conclude, therefore, that the sympathetic nerves which enter 

 these plexuses represent later connections and play only a secondary 

 part in their- development. 



From the above consideration it is evident that the vagus nerves 

 are of much greater importance in the development of the sympathetic 



1) pyriform = piriformis B.N. A., birnförmig. Herausgeber. 



