The growth of the brain : a study of the nervous system in relation to education / by Henry Herbert Donaldson.

  • Henry Herbert Donaldson
Date:
1909
Catalogue details

Licence: Public Domain Mark

Credit: The growth of the brain : a study of the nervous system in relation to education / by Henry Herbert Donaldson. 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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    AN I\TK(H)r(TK)N TO THK S'lTDV OK (IKOWTH. 2} one, tlie two nuclei unite to form a sinf][lc nucleus, and thus nioclified, the fertilised ovum or egg begins to grou'. The first indication of such growth is a division of the eg'^ into a number of cells, without much enlarge- ment of the total mass. This is apparentl)' the arrangement of the cell substance best suited for vigorous nutrition, and as the increase in bulk depends on nutritive processes, the importance of it is plain.' Later the nutritive conditions . 2.—Segmentation of a mammalian ovum. (/, /?, c, semi- diagrammatic X 170 diam. (Allen Thomsen, after v. Bene- den, Ouain's A/id/o/jty) ; d. Section of the ovum of the rabbit during the later stages of segmentation (E. v. lieneden, Ouain's Anatomy) ; «YA'=ectoderm ; cnto—^ entoderm. improve, and with this improvement the size of the mass increases. The processes which lead to subdivision arc first evident in the nuclear structures, which become the seat of complicated but, at the same time, perfectly order!}- changes. As a result, the constituents of the nucleus divide into two portions which separate from one another, the surrounding cytoplasm gathers about the respective daughter-nuclei, and these two portions then become marked off by the cell-membrane ; thus, in the place of one cell, two cells are now present. B)- cell- ' Sachs, Flora, 1893.