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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    division occurring in this way, and accompanied by changes in the size and form of the elements, the com- plex individual is built up. What is thus accomplished in the case of man is roughly indicated by the following calculations:—Ac- cording to the estimate of C. Francke,^ there are, in the entire body of a full-grown person, a number of fixed cells represented by 4,000,000,000,000. The cells in the blood are not fixed, and for these the best calculations give 22,500,000,000,000, or, in the entire body, a total of 26,500,000,000,000 cells. This number may appear surprisingly large, but it must be remembered that there are in a cubic millimeter 1,000,000,000 cubic [jl (the micron=ju being O'OOi of a millimeter, and the unit adopted by histologists in micrometry) ; so that if each cell in the human body had but the volume of one cubic /(, the whole number could be condensed into 22,500 cu. Fu;. V —Represeiuirifr a cube „^ . , ^_ ^^, ^ 2-8 cm. long on each edge, ^m-' ^r 22-5 cu. cm., not a This cube could contain very large mass, since it is 26 500,000,000 000 cells pro- i-epi-esented b}^ a cube length vided each cell had a volume ^ . -^ „. . of I cubic micron, the who.se edge is 2-.S cm. (hlg. 3-) micron being the unit of These facts can be expressed measure cniplovcd by histo- . ^.,, ,, r u- i -n ]^„\^xs ' in still another form which will indicate the average size of the cells. A man weighing 150 lbs.—the average specific gravit}' of his body being taken as ro30—would have a volume of 66,200 cu. cms. As stated above, all the cells of the body might be contained in 225 cu. cm., provided each cell had a volume of only i cu. /<. V>y ' Y\?i\\Q\.(t, Die nioiscJilichc Zellc, 1891.