Development of the Meninges in the Chick.

Abstract

Harvey and Burr 1 , 2 have presented evidence that in the salamander, the neural crest was a necessary requisite for the formation of the leptomeninx. We have continued the study by means of chorioallantoic grafts in the chick. Two series of operations were performed by Dr. Van Campenhout. In the first, the prosencephalon of 50-hour chicks was transplanted adjacent to an allantoic vessel of a 9-day host and allowed to develop from 7 to 9 days. In the second, an entire segment of the thorax or abdomen from a 50- to 98-hour chick was transplanted on the chorio-allantoic membrane of 9-day hosts. These also were permitted to develop for a period of approximately 9 days. Our knowledge of the distribution of the neural crest cells indicates that at the time of operation no such cells have as yet reached the region of the forebrain. It could then be transplanted devoid of neural crest investiture. On the other hand, during the period immediately following the 50-hour incubation period, the neural crest has begun its migration about the spinal cord in the thoracic and abdominal segments. Thus we have the nervous system transplanted without neural crest in the first series and with neural crest in the second. Since all the other conditions were as nearly constant as possible any difference in the structure of the meninges could be attributed to the presence or absence of the neural crest.

The material from the above experimental procedure was prepared for microscopic study using chiefly the Masson stain. A critical examination shows that there is a marked difference in the membranous investment of the nervous system in the 2 series. In series one, without neural crest, the nervous system is surrounded by a series of fibrous laminae of obvious mesenchymal origin.