Paper - The development of the neural folds and cranial ganglia of the rat

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Adelman HB. The development of the neural folds and cranial ganglia of the rat. (1925) J. Comp. Neurol. 39(1): 19-171.

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This historic 1925 paper by Adelman described development of the early rat central nervous system and cranial ganglia.

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1915 Normal Albino Rat | 1915 Abnormal Albino Rat | 1915 Albino Rat Development | 1921 Somitogenesis | 1925 Neural Folds and Cranial Ganglia | 1933 Vaginal smear | 1938 Heart

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The Development of the Neural Folds and Cranial Ganglia of the Rat

Howard B. Adelmann

Department of Histology and Embryology, Cornell University, Ithaca, New Pork

Six Text Flgures and Twenty-Four Plates (Ninety-Five Figures)


It is a pleasure to acknowledge here the generous help of many friends. I am especially indebted to Prof. B. F. Kingsbury for constant advice and encouragement. It was he who suggested that I take up the work. Miss Janet A. Williamson kindly allowed me to use the models of the head of the rat which she constructed as well as a number of important series prepared by her. I also wish to thank Dr. Fred W. Stewart for the use of many excellent series of older embryos, and finally I should like to express my appreciation of the skill and unfailing courtesy of Miss F. Louise Duhring, who collected the material at The Wistar Institute. I am indebted to the Mrs. Dean Sage Research Fund, which bore the expenses of the investigation.

Draft Version Only


The early development of the neural tube and cranial ganglia has been investigated with some degree of completeness in only a few mammalian forms. There are, it is true, numerous accounts based upon the study of very limited material and the literature abounds with observations on the development of the neural tube and cranial ganglia made incidentally in works dealiiig with the general anatomy of the embryo. Bartelmez ('22, '23) has recently called attention to the paucity of our knowledge of this subject and has himself contributed greatly to our understanding of the early development of the neural folds and sensory anlagen of the human embryo.

The reasons for the scarcity of work dealing with the development of these structures in the Mammalia are obvious, since the difficulties attending the collection of complete series of mammalian embryos are well known. In studying human embryos investigators have been especially handicapped both by the scarcity of the material at their command and the faulty preservation which such embryos frequently exhibit due to the circumstances under which they are obtained.

There are still many features of the development of the neural crest and cranial ganglia in mammals upon which additional observations are much needed, and many inter- esting questions are still at issue. Workers on the lower forms, especially the Ichthyopsida, seem to be quite generally agreed that the epibranchial and lateral-line placodes contribute liberally to the formation of the cranial ganglia, but the occurrence of such placodal contributions in Mammalia is still an open question. Several authors have described the formation of mesenchyme (mesectoderm) from neural-crest elements in the mammal, and this has been denied by others. The anterior limit of the neural crest, a point of the greatest theoretical importance, has not yet been clearly determined in the mammal. Further observations are needed on the exact mode of origin of the crest and its relation to the neural plate and ectoderm.

In addition, there are problems in connection with the individual cranial ganglia which have not been adequately solved. What, for instance, is the exact mode of origin of the ophthalmic ramus of the trigeminus in the mammal? Does it arise, as Belogolowy ('10) suggests for the bird, as a condensation of diffuse neural crest proliferated from the mid-brain; by placodal proliferation, as some have maintained; or by forward growth from the main ganglionic mass of the trigeminus? Is there a separate profundus anlage of the trigeminus, as Schulte and Tihey (’15) indicate in the cat? Does the acoustic ganglion split off from a common acoustico-facial mass? Is it increased by proliferation from the walls of the otic vesicle? Is it true that the ganglia petrosum and nodosum have an origin distinct from that of the rest of the IX-X anlage, as Streeter (’04) thought possible?

The answers to some of the questions proposed above depend upon a knowledge of the subdivisions of the early neural plate and tube.

The foregoing brief outline makes clear, I think, the desirability of further studies. The writer has taken advantage of the facilities bf The Wistar Institute for the collection of a close series of rat embryos upon which a study of the above problems was made. He has tried to keep constantly in mind the actual growth transformations of the whole head, in which the developing ganglia are involved. The early history of the neural plate and tube has been followed, inasmuch as an understanding of the growth and subdivisions of the early neural tube is necessary in studying the relations of the ganglia.

Material and Methods

This paper is based upon the study of more than 200 series of embryos of the white rat, Mus norvegicus albinus. The rats were obtained from The Wistar Institute and most of the uteri were removed and fixed there. The embryos were fixed at three-hour intervals from the nine-day-twelve-hour stage until thirteen days ; after that at less frequent intervals. Of many of the younger, more critical stages, two or even three litters were sectioned. Considerable variation was found in some uteri. Most of the material was fixed in Bouin’s fluid; a few were fixed in Carnoy’s and some of the older stages were fixed in Zenker’s, Helly’s or vom Rath’s picro-aceto-osmic-platinic chloride mixture by Doctor Stewart. All the material was cleared in xylene or toluene and embedded in paraffin. Most of the younger embryos were cut at 7.5 um, others at 10. Most of the embryos were stained in toto with Mayer's HC1 carmine, a few in Delafield's haematoxylin. A few were stained on the slide in iron haematosylin or in haematoxylin and orange G. Models were made of several stages by the Born method.

It was found best to section the younger stages in utero, after carefully cutting away the musculature. Since early embryos of the rat are oriented in a perfectly definite fashion with respect to the axes of the uterus, it is possible to secure favorable planes of sections in a large majority of cases, even of embryos sectioned in utero, up to a certain stage. The orientation of the embryos in the uterus has been found to be essentially as described by Widakowich ('09, '11). At eleven days and after, it is quite feasible to remove embryos from the uterus so that they may be oriented for cutting.

Throughout this paper the age will, so far as possible, be given in somites, since that method is most reliable. The Cornell collection now contains one or more embryos of every somite number from 1to 32, besides a large number of older embryos beginning with 34 somites. Of many stages trans- verse, sagittal, and frontal series are available, making it possible to check up carefully the interpretation of series.

Cite this page: Hill, M.A. (2021, October 21) Embryology Paper - The development of the neural folds and cranial ganglia of the rat. Retrieved from

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