AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOGRAPHIC SERVICE, AUGUST 15 



DISTRIBUTION OF THE SPINAL NERVES IN POLISTO- 



TREMA AND SOME SPECIAL STUDIES ON THE 



DEVELOPMENT OF SPINAL NERVES 



WILLIAM F. ALLEN 

 From the Department of Anatomy of the Universities of Minnesota and Oregon 



THIRTY-FIVE FIGURES 



CONTENTS 

 Introduction 137 



Material and methods 138 



Manner of distribution of the motor and sensory spinal nerve fibers in adults 



and embryos of various vertebrates 138 



1. Comparison of the two extremes, Amphioxus and Petromyzon, with 



mammals 138 



2. Conditions in various regions of adult Polistotrema 140 



3.' Embryonic arrangement in Polistotrema 156 



4. Adult and embryonic conditions in Squalus acanthias 158 



5. Arrangement in the turtle and pigeon embryos 168 



Possible causes for the union of the motor and sensory spinal rami in all ver- 

 tebrates above the cyclostomes 168 



1. Mechanical factors 170 



2. Chemical attraction (chemotropism) 171 



Distribution and possible significance of certain ganglion cells on the course 



of the spinal and vagus nerves of Polistotrema 172 



1. Peripheral spinal nerve cells 173 



2. Vagus nerve cells 177 



Sensory and motor innervation of the M. cordis caudalis 178 



Muscle spindles 181 



Remarkable size of certain motor fibers in the spinal nerves. . . ". 182 



Summary and conclusions '. 184 



Literature 188 



INTRODUCTION 



This paper is the result of a continuation of a study of some 

 problems suggested from the distribution and development of 

 the peripheral and central nervous system in Polistotrema 

 (Bdellostoma) . A recent publication dealt with the origin of 

 the tela choroidea of the fourth ventricle and the causes con- 



137 



