Archive image from page 44 of The development of the chick. The development of the chick : an introduction to embryology . developmentofchi02lill Year: 1936 THE EGG 27 :m tK fully ripe follicle and is completed after ovulation in the oviduct while the ovum is being fertilized. The origin of the primitive ova, their multiplication and the formation of the primordial follicles is described in Chapter XIII. In the young chick all the cell cords and cell nests (de- scribed in Chapter XIII) become converted into primordial follicles. During the egg-laying period there is a continuous process of gr
Archive image from page 44 of The development of the chick. The development of the chick : an introduction to embryology . developmentofchi02lill Year: 1936 THE EGG 27 :m tK fully ripe follicle and is completed after ovulation in the oviduct while the ovum is being fertilized. The origin of the primitive ova, their multiplication and the formation of the primordial follicles is described in Chapter XIII. In the young chick all the cell cords and cell nests (de- scribed in Chapter XIII) become converted into primordial follicles. During the egg-laying period there is a continuous process of growth and ripening of the primordial follicles, which takes place successively; the immense majority at any given period remain latent, but all stages of growth of egg follicles may be found in a laying hen. A primordial follicle consists of the ovum surrounded by a single layer of cubical epithehal cells (granulosa or follicle cells); the fibers of the adjacent stroma have a concentric arrangement around the folUcle forming the theca folHculi (Fig. 6 Str.). The ovum itself is a rounded cell with a large nucleus placed excentri- cally so as to define a primary axis of the ovum. In the pro- toplasm on one side of the nucleus is a concentrated mass of protoplasm, the yolk-nucleus, from which rays extend, and minute fatty granules. HoU derives the follicular cells in birds from the stroma, but on insufficient grounds. According to D'Hollander, they are derived, like the primitive ova, from the germi- nal epithelium, in which he agrees with the majority of his predeces- sors. He states that the period of ' multiplication of the ovogonia ends about the time of hatching; that the period of grovth of the ovocytes begins at about the fourteenth day of in- cubation (seven days before hatching), and before the formation of the primordial follicle, which begins on the fourth day after hatching. Thus the periods of multiplication and growth overlap. Although the nucleus (germinal vesicle of
Size: 1599px × 1251px
Photo credit: © Actep Burstov / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: 1930, 1936, archive, book, bookauthor, bookdecade, bookpublisher, booksubject, bookyear, drawing, embryology, historical, history, illustration, image, lillie_frank_rattray_1870_1947, new_york_henry_holt, page, picture, print, reference, vintage
