File:A text-book of embryology for students of medicine (electronic resource) (1907) (20165955299).jpg

Title: A text-book of embryology for students of medicine (electronic resource)
Identifier: b21286991 (find matches)
Year: 1907 (1900s)
Authors: Heisler, John Clement; Waterstone, David, former owner; Duke-Elder, Stewart, 1898-1978, former owner; University College, London. Library Services
Subjects: Embryology; Embryology
Publisher: Philadelphia : W. B. Saunders Company
Contributing Library: UCL Library Services, University College London (UCL)
Digitizing Sponsor: Jisc and Wellcome Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
THE SPERMATOZOON. 21 minal filament. At the anterior end of the axial fiber is a small body, the end-knob (not shown in the figure). The power of locomotion which the spermatozoon exhibits is conferred by the vibratile movement of its tail, accompanied by a rotation about its long axis through an arc of 90 degrees. The rate of progression is about 0.05 or 0.06 mm., or its own length, per second. Spermatozoa possess remarkable vitality, remaining active in the male genital tract for several days after death. In the genital passages of the female, they may retain their activity for several weeks, and when mounted and protected from evaporation they have been known to show vibratile motion after the lapse of nine days (Piersol). Weak alkaline solu- tions render them more active, while acids, even quite dilute, destroy fhem. The spermatozoa of the bat, being deposited in the female genital passages in the autumn, retain their power of fecundating ova until the following spring. Spermatogenesis.—The details of spermatozoon-formation, or spermatogenesis, vary in different animals. A cross sec- tion of a seminiferous tubule of a mammal (Fig. 3) shows a layer of cuboidal cells called parietal cells, lying in contact
Text Appearing After Image:
a Fig. 3— Section of testicle of musk-rat; seminiferous tubule seen in cross section: a, wall of tubule; b, parietal cells ; c, mother-cells ; d, spermatoblasts. with the basement membrane of the tubule wall. This layer consists of the so-called Sertolli's columns, or sustentacular cells, and of the spermatogenic cells or spermatogonia. The sustentacular cells are merely supporting ; the spermatogenic cells give rise to the spermatozoa.

Note About Images