NOTES ON THE DEVELOPMENT OF THE SYMPA- 

 THETIC NERVOUS SYSTEM IN THE 

 COMMON TOAD.^ 



By Walter C. Jones, M. D. 



With twelve figures. 



The work which forms the basis of this paper was done in 

 1898-1900, at the Zoological Laboratory of Northwestern Uni- 

 versity, Evanston, Illinois, and was presented in part fulfillment 

 for the degree of Master of Arts. Circumstances prevented the 

 immediate preparation of the results for publication. In the 

 considerable interval to the present, only one paper, as far as I 

 know, has been published, dealing with the development of the 

 sympathetic nervous system; this paper, by Hoffmann, 1902, 

 is briefly noticed in my review of the literature. The writer 

 wishes to thank Professor Wm. A. Locv, Director of the Lab- 

 oratory, for invaluable help in the work and in the revision of 

 the manuscript. 



The earlier view in regard to the origin of the sympathetic nerv- 

 ous system was that advanced by Remak, to the effect that it arose i?i 

 situ from the mesoblast. Balfour, after his researches on elasmo- 

 brauch fishes ('78), brought forward a new view, namely, that the sym 

 pathetic nervous system arises from the epiblast iu connection with the 

 spinal and with certain of the cranial nerves. He claimed that the sym- 

 pathetic ganglia of the trunk region "are at first simply swellings on 

 the main branches of the spinal nerves." Subsequently, these swell- 

 ings are removed each from its respective nerve, retaining, however, 

 fibrous connections with the nerve through a short branch, which forms 

 a ramus comnninicatis . They appear at first to be independent, becom- 

 ing united later by commissures, and forming a continuous cord on ei- 

 ther side. 



1 Contribution from the Zoological Laboratory of Northwestern University, 

 William A. Locy, Director. 



