HYPOTHESES OF MOLECULAR STRUCTURE 77 



According to Nageli l , the ultimate elements of which organized bodies 



are composed, i.e. the minute particles between which water penetrates 



when swelling takes place, are not molecules, but molecular aggregates, 



termed by htm ' micellae V These micellae may be built up of molecules, 



groups of molecules, or be even more complex in nature. They have 



a definite structure, and like crystals, when broken, the fragments retain the 



properties of the whole, while the same is also the case when a micella or 



micellar structure composed of homogeneous micellae increases in size. In 



a crystalloid, or an artificial cellulose membrane, the micellae are all of the 



same kind, but in organized bodies, according to Nageli, the micellae 



probably vary in size and quality, while in the protoplasm very hetero- 



geneous elements are certainly aggregated together (Sect. 78). (Cf. Fig. 3.) 



The micellae may differ much in shape, while similar and dissimilar 



micellae may be combined together in all manner of 



ways. By their behaviour when dried, and the appear- 



ances presented under polarized light, &c., Nageli was, 



however, led to conclude that the micellae of organized 



bodies are in general crystalline, or at least polyhedral* 



and that in solid bodies the axes of the micellae are 



arranged in a definite manner, either parallel to one 



another, or in a radial arrangement like the radial 



acicular crystals which form a sphaerocrystal. Nageli 



later (1879) supposed that the micellae may combine in 



various ways to form units of higher ordinal value, and 



concluded that in colloidal substances the micellae unite p 



to form a meshwork in three dimensions. * r 



Why Nageli should postulate a power of swelling 

 as a general property of micellae is not easy to see, for 

 the groups of molecules which may form the elemental units of an organ- 

 ized structure capable of swelling may themselves be unable to imbibe 

 water 3 . If the living physiological units are, in correspondence with their 



Na 



1 Nageli, Die Starkekorner, 1858, p. 322 ; Uber die krystallahnlichen Proteinkorper, 1862, Bot. 

 Mitth., Bd. I, p. 217; li. d. inneren Bau d. veg. Zellmembran, 1864, ibid., pp. i and 46 ; Theorie 

 der Gahrung, 1879, p. 121 ; Theorie d. Abstammungslehre, 1884, p. 35! Nageli und Schweiv 

 Das Mikroskop, 1877, 2. Aufl., p. 532. 



* Nageli und Schwendener, Das Mikroskop, 1877, I.e., p. 494. Nageli at first gave i 

 micellae the name of molecules, already appropriated in Chemistry. A micella is typically composed 

 of a group of molecules, but may be more or less complicated than this. The term lagm 

 (Osmot. Unters., 1877, p. 32) corresponds to Nageli's micella, and the latter term may thereto 

 adopted. A molecular combination of fixed and definite character has been termed by * 

 (Theorie der Gahrung, 1879, p. 122) a pleon. 



> Water of crystallization is here disregarded, but it may nevertheless, under particular c< 

 ditions, be held in a similar manner to that in which imbibed water is held. In general, a distinct: 

 can be made between water of crystallization and water of imbibition (constitutional water and water 

 of adhesion). Pfeffer, Osmot. Unters., 1877, p. 35 J Nageli, Theorie d. Gahrung, 1879, P- "9- 



