HYPOTHESES OF MOLECULAR STRUCTURE 77 



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

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

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

 termed by him ' 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 FIG - 3-. Schematic re- 



presentation of molecu- 



to form a meshwork in three dimensions. 



Why Nageli should postulate a power of swelling dener - 

 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 :! . If the living physiological units are, in correspondence with their 



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

 Mitth., Bd. I, p. 217; \J. 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 Schwendener, 

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



2 Nageli und Schwendener, Das Mikroskop, 1877, I.e., p. 424. Nageli at first gave to the 

 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 'Tagma' 

 t^Osmot. Unters., 1877, p. 32) corresponds to Nageli's micella, and the latter term may therefore be 

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

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



3 Water of crystallization is here disregarded, but it may nevertheless, under particular con- 

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

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

 of adhesion). Pfeffer, Osmot. Unters., 1877, p. 35 : Nageli, Theorie d. Gahrung, 1879, p. '-'9. 



