OEGANIC MATTEE. 21 



plex compounds composing organic bodies — compounds in 

 which there are various cross affinities leading to a state 

 of chemical tension — this extreme difference in the molecular 

 mobilities must be an important aid to molecular re-arrange- 

 ments. In short, we are here led by concrete evidence to the 

 conclusion which we before drew from first principles, that 

 this great unlikeness among the combined units must facili- 

 tate differentiations. 



§ 8. A portion of organic matter in a state to exhibit those 

 phenomena which the biologist deals with, is, however, some- 

 thing far more complex than the separate organic matters 

 we have been studying ; since a portion of organic matter in 

 its integrity, contains several of these. 



In the first place, no one of those colloids which make up 

 the mass of a living body, appears capable of carrying on 

 vital changes by itself : it is always associated with other 

 colloids. A portion of animal-tissue, however minute, almost 

 always contains more than one form of protein-substance : 

 different chemical modifications of albumen and gelatine are 

 present together, as well as, probably, a soluble and insoluble 

 modification of each ; and there is usually more or less of 

 fatty matter. In a single vegetal cell, the miniite quantity 

 of nitrogenous colloid present, is imbedded in colloids of the 

 non-nitrogenous class. The microscope makes it at once 

 manifest, that even the smallest and simplest organic forms 

 are not absolutely homogeneous. 



Further, we have to contemplate organic tissue, formed 

 of mingled colloids in both soluble and insoluble states, as 

 permeated throughout by crystalloids. Some of these crys- 

 talloids, as oxygen,* water, and perhaps certain salts, are 

 agents of decomposition ; some, as the saccharine and fatty 



* It will perhaps seem strange to class oxygen as a crystalloid. But inasmuch 

 as the crystalloids are distinguished from the colloids by their atomic simplicity, 

 and inasmuch as sundry gases are reducible to a crystalline state, we are justi- 

 fied in so classing it. 



