18 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
U. Spinal nerves : : é ¢ 
1. Third spinal nerve ¢ 
2. Second spinal nerve g 
3. First spinal nerve . ; — 
4. Connections of first three spinal nerves with sympathetic. 9 
V. General considerations on nerve XII and the spinal nerves . 9 
W. General summary 9 
Bibliography 10 
Explanation of plates 10 
A. INTRODUCTION. 
It is now generally recognized that the comparative anatomy of the 
nervous system can not be profitably studied without recourse t 
microscopic analysis in the peripheral region as well as in the centra 
organs. It is further recognized that, for their final explanation, thi 
highly complex nervous organs of mammals, including man, mus 
await the revisions and additions which such a method of study 
applied to the lower vertebrates, will suggest for their interpretation 
Inasmuch as the nervous system is essentially a correlating structure. 
it follows naturally that changes in its mechanism should be studie. 
in connection with a study of the correlated organs and function: 
This gives to the study of the nervous system a broader biologic: 
significance than is possessed by other organs. But this relation ad¢. 
much to the technical difficulties and makes it almost impossible t 
bring within the scope of a single research the complete analysis « 
even a single form. The shortcomings of the present study from thé 
point of view are recognized by the author. However, in the methoc 
pursued, he has had constantly in mind the larger problem, whic 
does not recognize the arbitrary distinction between central and p) 
ripheral nervous systems. In fact, he has already collected mut 
material and information on the central nervous system of Anoli 
but it seems advisable to reserve that material for a more comple! — 
account of the Anolis brain. The present investigation is carried fy 
enough toward the nerve centers to articulate easily with such a stud 
A large part of this work was done a number of years ago in tl! 
Zodlogical Laboratory of Harvard University. Since then it has be! 
continued in the Laboratory of Histology and Embryology of t | 
University of Nebraska, College of Medicine. In this connection) 
wish to acknowledge my gratitude to Dr. E. L. Mark for placing eve 
