MOLECULAR STRUCTURE OF ORGANISED BODIES. 33 



does not take place equally in all three dimensions of space 

 and from their double refraction Naegeli inferred the form 

 of the micellae. The unequal swelling-up, he considered, 

 indicated that the micellae were anisometric, the direction 

 of least expansion corresponding to the direction of the 

 longest axis of the micellae, for it is in this direction that 

 their attraction for each other would be greatest and for 

 water least. As to the double refraction, he found that when 

 the bodies exhibiting it (starch-grains, cell- walls, crystalloids), 

 were subjected to strain or torsion, or were made to swell-up, 

 they did not lose it. He argued that, since the optical pro- 

 perties of these organised structures are apparently not de- 

 pendent, like those of a crystal or of a piece of glass, upon the 

 relative position of their constituent particles, they must be in- 

 herent in the particles themselves. Each micella, then, possesses 

 the optical properties of an anisotropic crystal. Naegeli 

 concluded, therefore, that the micellae are crystals, and from 

 the interference colours observed with the polariscope, he 

 inferred that they must be biaxial crystals, and assigned 

 to them, as a probable form, that of parallelopipedal prisms 

 with rectangular or rhomboid bases. 



Such is, very briefly, the " micellar theory " of the struc- 

 ture of organised bodies developed by Naegeli from his 

 observations on cell-walls, starch-grains, and on the proteid 

 crystalloids which are found more especially in seeds. He 

 was unable, however, to apply it in its entirety to protoplasm, 

 for the optical properties of protoplasm are not such as to 

 indicate that its micellae are crystalline. 



Strasburger has given an altogether different account of 

 the various phenomena described above. In the first place 

 he rejects the idea of the aggregation of the chemical mole- 

 cules into micellae. He is of opinion that the force which 

 binds together the molecules is of a chemical as opposed 

 to a physical nature, that they are held together not by 

 cohesion but by chemical affinity : he regards them as being 

 linked together, probably by means of multivalent atoms, 

 into molecular networks, the water present being retained 

 in the meshes by intermolecular capillarity. 



v. 3 



