284 ALBERT KUNTZ 



the writer's observations on the histogenesis of the sympathetic 

 nervous system in mammals, and to point out certain morphogene- 

 tic differences in the development of the sympathetic system in 

 birds and in mammals, with a view to their phylogenetic signifi- 

 cance. 



Birds and mammals have become specialized along divergent 

 lines. Their special habits of life have brought about modifica- 

 tion in the course of ontogeny as well as in adult structure. The 

 sympathetic nervous system, which is concerned primarily with 

 the control of the purely vegetati\e functions, has not escaped the 

 modifying influence of specialized habits. It is hoped, therefore, 

 that a more exact knowledge of the development of the sympa- 

 thetic nervous system in birds may throw some new light on the 

 problems involving the structural and the functional relationships 

 of the sympathetic system to the central nervous system. 



Inasmuch as the literature bearing on the development of the 

 sympathetic nervous system has been reviewed by the writer in 

 a recent paper, 2 only such references will be made to the liter- 

 ature in this paper as seem to be necessary. 



The observations set forth in the following pages are based on 

 embryos of the chick. The embryos were fixed in chrom-aceto- 

 formaldehyde. The sections were cut to a thickness of 10 micra 

 and stained by the iron-ha^matoxylin method. This method, as 

 indicated in the earlier paper, was found best adapted for pur- 

 poses of this research. 



OBSERVATIONS 



1. Sympathetic trunks 



(a.) Introductory. — His, Jr. ('97) called attention to the fact that 

 in the chick two pairs of sympathetic trunks arise in the course of 

 ontogeny. These he has designated as the "primary" and the 

 ' ' secondary ' ' sympathetic trunks. According to his observations, 

 the primary sympathetic trunks arise about the close of the third 



2 The development of the sympathetic nervous system in mammals. Journal 

 of ( 'tmiparative Neurology and Psychology, vol. 20, no. 3. 



