. The biology of the cell surface. Cytology. GENERAL PROPERTIES OF THE ECTOPLASM Red blood corpuscles are discs, measuring seven to eight by two microns; they thus possess a large surface area, the sum of which amounts in an adult man of 78 kilograms, according to one estimate, to 3840 square meters. Hart- ridge^ has suggested that the shape of the red blood corpus- cle is the best possible one for insuring easy oxygen-intake. No one can object to the proposition that oxygen to enter a cell must cross the cell-boundary. Even on the theory that in oxygen-consumption only the most deeply located
. The biology of the cell surface. Cytology. GENERAL PROPERTIES OF THE ECTOPLASM Red blood corpuscles are discs, measuring seven to eight by two microns; they thus possess a large surface area, the sum of which amounts in an adult man of 78 kilograms, according to one estimate, to 3840 square meters. Hart- ridge^ has suggested that the shape of the red blood corpus- cle is the best possible one for insuring easy oxygen-intake. No one can object to the proposition that oxygen to enter a cell must cross the cell-boundary. Even on the theory that in oxygen-consumption only the most deeply located structures of the cell, nucleus or otherwise, are concerned, the oxygen enters the cell by way of the cell-surface. Rea- soning by analogy we may say that just as there exist special structures as gills and lungs to obtain oxygen, so in cells generally the modified surface permits easy access of oxygen. These surface-modifications are delicate prolongations. It is also interesting to note that pigment granules, said to be carriers of oxygen, line up at the cell surface. Oxidation means liberation of heat. The heat is lost by the cell-surface. Here again the cell-surface is admir- ably constructed for the rapid conduction and radiation of heat. Since heat is produced when colloids take up water and also when they liquefy, it may be that cell-surfaces in breakdown through swelling and liquefaction liberate heat. Another fundamental property of living substance is conduction. Any living cell when stimulated has the capa- city to transfer the effect of this stimulus. The degree of conduction constitutes one of the chief differences that dis- tinguish animals from plants. In animals conduction is the function of the nervous system, which possesses this property, general to all cells, in the highest degree. Now among other characteristics of nerve cells we note an extreme differentiation of the ectoplasm, as has been stated. Nerve cells show one or more processes, some of Hartridge,
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