The development of the human body : a manual of human embryology / by J. Playfair McMurrich.

  • McMurrich, J. Playfair (James Playfair), 1859-1939.
Date:
1914
Catalogue details

Licence: Public Domain Mark

Credit: The development of the human body : a manual of human embryology / by J. Playfair McMurrich. 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 DEVELOPMENT OF THE HUMAN BODY. INTRODUCTION. Somewhat more than seventy years ago (1839) one of the funda- mental principles of biology was established by Schleiden and Schwann as the cell theory. According to this, all organisms are composed of one or more structural units termed cells, each of which, in multicellular organisms, maintains an individual existence and yet contributes with its fellows to the general existence of the indi- vidual. Viewed in the light of this theory, the human body is a community, an aggregate of many individual units, each of which leads to a certain extent an independent existence and yet both contributes to and shares in the general welfare of the community. To the founders of the theory the structural units were vesicles with definite walls, and little attention was paid to their contents. Hence the use of the term cell in connection with them. Long before the establishment of the cell theory, however, the existence of organisms composed of a gelatinous substance showing no indica- tions of a definite limiting membrane had been noted, and in 1835 a French naturalist, Dujardin, had described the gelatinous material of which certain marine organisms (Rhizopoda) were composed, terming it sarcode and maintaining it to be the material substratum which conditioned the various vital phenomena exhibited by the organisms. Later, in 1846, a botanist, von Mohl, observed that living plant cells contained a similar substance, upon which he