The present review is based on the data of the literature, and on the personal experience gained by the author in recent years by studying the histogenesis of spinal ganglia. Probably, the reader will find more than one gap in the biblio graphy. The author would like to point out that in no case are such gaps due to the voluntary omission of any information, interpretations, or views. The gaps are due only to the difficulties met in trying to master such a vast literature consisting of so many contributions which have appeared over more than a century. An endeavour has been made to report not only the morphological data, but also, whenever possible, information derived from histochemical and biochemical studies. 11. Origin 01 the Spinal Ganglia Before 1868 it was generally thought (see, e.g., Remak, 1851; Bidder and Küpffer, 1857) that the spinal ganglia arise from the mesoblast of the protoverte brae (old term for somites). In 1868 His showed that the nerve cells of the spinal ganglia take their origin from the ectoderm, and more precisely from a thin band of ectoderm (Zwischenstrang, neural crest) flanking each side of the neural plate (Fig. 1 a) and interposed between it and the somatic ectoderm (Hornblatt). On this subject His (1879) wrote in a later paper " ... die spinalen Ganglien ... aus einem schmalen Substanz streifen hervorgehen, welche zwischen der Medullarplatte und dem Hornblatte gelegen ist und dessen Material ich als Zwischenstrang bezeichnet habe".

I. Introduction

II. Origin of the spinal ganglia
III. Undifferentiated cells
IV. Development of the nerve cell
V. Degenerative events in developing ganglia
VI. Development of satellite cells, interstitial spaces, and blood vessels
VII. Concluding remarks
Summary
Acknowledgements
References.