Note 55 — Chapter II · ON MAGNITUDE

For various calculations of the increase of surface due to histological and anatomical subdivision, see E. Babak, Ueber die Ober­flächenent­wicke­lung bei Organismen, Biol. Centralbl. XXX, pp. 225–239, 257–267, 1910. In connection with the physical theory of surface-energy, Wolfgang Ostwald has introduced the conception of specific surface, that is to say the ratio of surface to volume, or S ⁄ V. In a cube, V = l3 , and S = 6l2 ; therefore S ⁄ V = 6 ⁄ l. Therefore if the side l measure 6 cm., the ratio S ⁄ V = 1, and such a cube may be taken as our standard, or unit of specific surface. A human blood-corpuscle has, accordingly, a specific surface of somewhere about 14,000 or 15,000. It is found in physical chemistry that surface energy becomes an important factor when the specific surface reaches a value of 10,000 or thereby.