32 LECTURE III. 



"organised " was extended, so as to include all bodies capable 

 of swelling-up. 



Now as to the explanation of this phenomenon. According 

 to Naegeli it is the expression of the taking up of a number 

 of particles of water between the solid^particles (termed by 

 him micella) of the organised body. ^That the absorption of 

 water is not effected by capillarity is inferred from the fact 

 that organised bodies are not porous. A perfectly dry cell- 

 wall, for example, is transparent, and this could not be the 

 case if any capillary interspaces existed between its micellae, 

 for, in the dry state of the wall, such interspaces would neces- 

 sarily be filled with air, and the wall would therefore be 

 opaque. In a dry cell-wall, then, the micellae are in contact 

 on all sides. When it takes up water, the water does not 

 enter into already existing spaces between the micellae, for 

 there are none; it must therefore penetrate between the 

 micellae, forcing them apart against the opposing force of 

 cohesion which tends to hold them together. 



These micellae of Naegeli's must by no means be con- 

 founded with chemical molecules ; they are aggregates of 

 larger or smaller numbers of chemical molecules. It must 

 also be pointed out that in a case of ordinary swelling-up, 

 the water does not penetrate into the micellae : when this 

 takes place the result is, as we shall find hereafter, that the 

 micellar structure is disintegrated. 



Upon these facts Naegeli founded a general theory of the 

 structure of organised bodies. He conceives them as con- 

 sisting of solid micellae, each of which is, under ordinary 

 circumstances, surrounded by a layer of water, the micellae 

 with their watery envelopes being held together by the fol- 

 lowing forces : (a) the attraction of the micellae for each other, 

 a force which varies inversely as the square of the distance 

 between them ; (fr) the attraction of each micella for the 

 water which surrounds it, a force which varies inversely as 

 some higher power of the distance ; and (c) the force which 

 holds together the ultimate chemical molecules of which each 

 micella consists. 



From the fact that the swelling-up of organised bodies 



