VI] OF THE GIBBS-THOMSON LAW 451 



energy and of adsorptive phenomena, in a somewhat old-fashioned 

 way; but even with this simphfying Uniitation we find them helpful, 

 throwing hght upon our subject. 



In the first place our preHminary account, such as it is, is already 

 tantamount to a description of the process of development of a 

 cell-membrane, or cell- wall. The so-called "secretion" of this cell- 

 wall is nothing more than a sort of exudation, or striving towards 

 the surface, of certain constituent molecules or particles within the 

 cell; and the Gibbs-Thomson law formulates, in part at least, the 

 conditions under which they do so. The adsorbed material may 

 range from an almost unrecognisable pellicle to the distinctly 

 differentiated "ectosarc" of a protozoon, and again to the develop- 

 ment of a fully-formed cell-wall, as in the cellulose partitions of a 

 vegetable tissue. In such cases, the dissolved and adsorbtive 

 material has not only the property of lowering the surface-tension, 

 and hence of itself accumulating at the 'surface, but has also the 

 prope^y of increasing the viscosity and mechanical rigidity of the 

 material in which it is dissolved or suspended, and so of constituting 

 a visible and tangible "membrane*." The "zoogloea" around a 

 group of bacteria is probably a phenomenon of the same order. 

 In the superficial deposition of inorganic materials we see the same 

 process abundantly exemphfied. Not only do we have the simple 

 case of the building of a shell or '"test" upon the outward surface 

 of a Hving cell, as for instance in a Foraminifer, but in a sub- 

 sequent chapter, when we come to deal with spicules and spicular 

 skeletons such as those of the sponges and of the Radiolaria^ we 

 shall see how highly characteristic it is of the whole process of 



* We may trace the first steps in the study of this phenomenon to Melsens, 

 who found that thin films of white of egg become firm and insoluble (Sur les 

 modifications apportees a I'albumine. . .par faction purement mecanique, C.R. 

 XXXIII, p. 247; Ann. de chimie et de physique (3), xxxiii, p. 170, 1851); and Harting 

 made similar observations about the same time. Ramsden investigated the same 

 subject, and also the more general phenomenon of the formation of albuminoid 

 and fatty membranes by adsorption, and found {i7it. al.) that on shaking white of egg 

 practically all .the albumin passes gradually into the froth; cf. his Koagulierung 

 der Eiweisskorper auf mechanischer Wege, Arch. f. Anat. u. Phys. {Phys. Ahth.), 

 1894, p. 517; Abscheidung fester Korper in Oberflachenschichten, Z. f. phys. Chern. 

 XLVii, p. 341, 1902; Proc. R.S. Lxxii, p. 156, 1904. For a general review of the 

 whole subject see H. Zangger, Ueber Membranen und Membranfunktionen, in 

 Asher-8piro's Ergebnisse der Physioloyie, vii, pp. 99-1(50, 1908. 



