THE DEVELOPMENT OF THE CYTOPLASMIC CON- 

 STITUENTS OF THE NERVE CELLS OF THE CHICK 



I. MITOCHONDRIA AND NEUROFIBRILS 



E. V. COWDRY 

 Associate in Anatomy, Johjis Hopkins University 



From the Anatomical Laboratory of the University of Chicago 



FIVE PLATES 



CONTENTS 



Introduction 389 



Literature 391 



Material and methods 396 



Mitochondria in early stages before the differentiation of neurofibrils: em- 

 bryos of to 14 somites 400 



Mitochondria and neurofibrils in later stages: embryos of 15 to 33 somites 402 



1. The stage of development at which the first neurofibrils are formed. . . . 402 



2. Type of cell in which neurofibrils first develop 403 



3. Region of cytoplasm in which neurofibrils originate 404 



4. Comparison of mitochondria and neurofibrils in embryological series: 



embryos of 19 to 31 somites 405 



Discussion 408 



1. Foundation of the theorj' that neurofibrils are developed from 



mitochondria 408 



2. Criticism of the theory 409 



3. The origin of neurofibrils 414 



Summary 416 



Bibliography 417 



INTRODUCTION 



The attention which has been focussed, during the last four 

 or i\ye years, upon mitochondria as fundamental components of 

 the cytoplasm of all cells has stimulated investigators in their 

 attempts to determine the relation which these bodies bear to 

 the activities of the cell and to the genesis of the cytoplasmic 

 constituents. Thus we find that Meves ('07, p. 403) was the 



389 



THE AMERICAN JOURNAI- OF ANATOMT, VOL. 1.5, NO. 4 

 JANUARY, 1914 



