174 ALBERT KUNTZ 



The present writer published the results of his earlier studies 

 on the development of the sympathetic nervous system in a 

 series of papers ('09-' 14). The conclusions drawn from these 

 studies regarding certain fundamental aspects of the problem, 

 especially with reference to certain portions of the sympathetic 

 system, differ widely from those of the earlier investigators. 

 Some of these conclusions have been substantiated by the work 

 of later investigators; some have suffered adverse criticism. 

 More mature study on the part of the writer has fortified his 

 confidence in the more fundamental conclusions, but has also 

 revealed errors of major and minor importance both in observa- 

 tion and interpretation. In view of the present status of the 

 problem, it has seemed desirable to undertake the present investi- 

 gation in order to correct certain errors referred to above, to 

 treat more adequately certain details of the problem which have 

 not been adequately studied hitherto, and to secure more accurate 

 and more extensive knowledge regarding the development of the 

 sympathetic nervous system in the human species. 



The observations recorded in this paper, except as otherwise 

 indicated, were made on human embryos included in the Carnegie 

 Embryological Collection. It is a real pleasure to express my 

 indebtedness to Dr. G. L. Streeter for placing this collection at 

 my disposal, for the opportunity of working in his laboratories, 

 and for the technical assistance of members of his staff in the 

 preparation of microphotographs. 



REVIEW OF LITERATURE 



The literature bearing on the development of the sympathetic ^ 

 nervous system in vertebrates has been reviewed more or less 

 fully by nearly all of the many investigators who have worked 

 in this field. It was reviewed also by the present writer in 1910. 



1 The writer appreciates the need of a terminology applied to this division of 

 the nervous system which could be accepted alike by anatomists and physiolo- 

 gists. However, inasmuch as the term 'sympathetic' was used in its broad 

 sense by the writer in his earlier papers, as well as b.y the majority of the more 

 recent investigators in this field, it seems advisable to use it in the same sense 

 in this paper. 



