A text-book of embryology for students of medicine / by John Clement Heisler. With 190 illustrations, 26 of them in colors.

  • Heisler, John C. (John Clement), 1862-1938.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of embryology for students of medicine / by John Clement Heisler. With 190 illustrations, 26 of them in colors. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    The fibrous wall of the follicle is lined by the membrana granulosa, which consists of many layers of epithelial cells; these^ at the point of contact with the ovum, project in such a manner as to surround it completely, the cellular envelope thus formed constituting the discus proligerus. The inner cells of the discus are arranged in two layers, the individual elements having their long axes radially directed. From the appearance of radial striation, conferred partly by this cir- cumstance, the inner zone has been called the zona radiata or zona pellucida, and the outer the corona radiata. The cavity of the Graafian follicle is filled with fluid, the liquor foUiculi. The stigma, or Mlum folliculi, a yellowish-white spot devoid of blood-vessels on the free surface of the Graafian follicle, indicates the point at which rupture will take place. After this event, which occurs when the ovum is ripe, the latter passes into the Fallopian tube. The ultimate origin of the Qgg is to be sought in that im- portant group of cells on the surface of the ovary to which Waldeyer gave the name germinal epithelium. This first appears at about the fifth week of intra-uterine life, as a localized thickening of the cells of the structure that subse- quently becomes the peritoneum. The thickened areas com- prise two longitudinal elevations on the dorsal side of the future abdominal cavity, one on each side of the median plane of the body; these are the genital ridges. Owing to the development of connective tissue beneath the epithelium, the ridges increase in thickness, and, with the progress of other changes, finally become, in the female, the ovaries. At about the sixth or seventh week—the germinal epithelium now consisting of several layers of cells instead of being a single stratum thick, as at first—cord-like processes, the sexual cords, or primary egg-tubes, or egg-columns, grow from the surface into the underlying connective tissue, carrying with them certain of the surface-cells (see Fig. 112). Conspicuous among these are the large sexual cells, or primitive ova; while smaller cells, likewise from the germinal epithelium, are also present. The sexual cords become divided into groups