[54] Proc. Psychical Soc. XII, pp. 338–355, 1897.
[55] 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.
[56] Though the entire egg is not increasing in mass, this is not to say that its living protoplasm is not increasing all the while at the expense of the reserve material.
[57] Cf. Tait, Proc. R.S.E. V, 1866, and VI, 1868.
[58] Physiolog. Notizen (9), p. 425, 1895. Cf. Strasbürger, Ueber die Wirkungssphäre der Kerne und die Zellgrösse, Histolog. Beitr. (5), pp. 95–129, 1893; J. J. Gerassimow, Ueber die Grösse des Zellkernes, Beih. Bot. Centralbl. XVIII, 1905; also G. Levi and T. Terni, Le variazioni dell’ indice plasmatico-nucleare durante l’intercinesi, Arch. Ital. di Anat. X, p. 545, 1911.
[59] Arch. f. Entw. Mech. IV, 1898, pp. 75, 247.
[60] Conklin, E. G., Cell-size and nuclear-size, J. Exp. Zool. XII. pp. 1–98, 1912.
[61] Thus the fibres of the crystalline lens are of the same size in large and small dogs; Rabl, Z. f. w. Z. LXVII, 1899. Cf. (int. al.) Pearson, On the Size of the Blood-corpuscles in Rana, Biometrika, VI, p. 403, 1909. Dr Thomas Young caught sight of the phenomenon, early in last century: “The solid particles of the blood do not by any means vary in magnitude in the same ratio with the bulk of the animal,” Natural Philosophy, ed. 1845, p. 466; and Leeuwenhoek and Stephen Hales were aware of it a hundred years before. But in this case, though the blood-corpuscles show no relation of magnitude to the size of the animal, they do seem to have some relation to its activity. At least the corpuscles in the sluggish Amphibia are much the largest known to us, while the smallest are found among the deer and other agile and speedy mammals. (Cf. Gulliver, P.Z.S. 1875, p. 474, etc.) This apparent correlation may have its bearing on modern views of the surface-condensation or adsorption of oxygen in the blood-corpuscles, a process which would be greatly facilitated and intensified by the increase of surface due to their minuteness.
[62] Cf. P. Enriques, La forma come funzione della grandezza: Ricerche sui gangli nervosi degli Invertebrati, Arch. f. Entw. Mech. XXV, p. 655, 1907–8.
[63] While the difference in cell-volume is vastly less than that between the volumes, and very much less also than that between the surfaces, of the respective animals, yet there is a certain difference; and this it has been attempted to correlate with the need for each cell in the many-celled ganglion of the larger animal to possess a more complex “exchange-system” of branches, for intercommunication with its more numerous neighbours. Another explanation is based on the fact that, while such cells as continue to divide throughout life tend to uniformity of size in all mammals, those which do not do so, and in particular the ganglion cells, continue to grow, and their size becomes, therefore, a function of the duration of life. Cf. G. Levi, Studii sulla grandezza delle cellule, Arch. Ital. di Anat. e di Embryolog. V, p. 291, 1906.