66 PRINCIPLES OF GENERAL PHYSIOLOGY 



Now, imagine the solid to be split up into smaller and smaller particles until 

 they become molecules. At this point the ordinary law of mass action will be 

 obeyed, since surface has no longer any existence. 



This example shows the justification of the view taken by B. Moore (1909, p. 520), that 

 there is no hard and fast line to be drawn between what he calls " molecular ' compounds, 

 which are the same as those called by others adsorption compounds, and true chemical 

 compounds. In the same way, as we shall see in the next chapter, there are all stages of 

 transition between colloids and crystalloids. This fact, however, does not alter the necessity 

 of taking into consideration the surface energy of colloids and matter in mass. It appears that 

 Moore desires to explain the phenomena of adsorption by chemical forces of an obscure and 

 indefinite kind (see p. 534 of the article referred to), whereas it is known that there is 

 present, and active, surface energy of various well-known forms, capable of satisfactorily 

 explaining the characteristics of these phenomena without any further assumptions. 



It seems to me that the well-known principle of logic called " William of Occam's Razor" 

 may legitimately be applied to such a case as the one before us ; " entia non sunt multipli- 

 candi praeter necessitatem. " Sir William Hamilton (1853, pp. 628-631) gives a more complete 

 form in his "Law of Parsimony": thus " Neither more, nor more onerous, causes are to be 

 assumed than are necessary to account for the phenomenon." 



As physiologists, we must take the chemical or physical explanation, according to which 

 leads further, when both are available. Some chemists appear to resent any explanation of a 

 phenomenon apart from a chemical one. As has been pointed out above, the ultimate source 

 of animal energy is almost entirely chemical, but, in the transportation and utilisation of this 

 energy, physical factors intervene, and these factors cannot be neglected without serious 

 error. Indeed, the same thing may be said of many non-vital processes, such as those of the 

 galvanic cell or those taking place in surface films. 



That there is, as Moore points out, a kind of stoichiometric relation between 

 the constituents of adsorption compounds is not to be wondered at, if we remember 

 the fact of adsorption saturation, that is, when the whole of the adsorbing surface 

 is covered with the adsorbed substance. This relationship is between the extent 

 of surface and the amount of compound formed and is not stoichiometric in the 

 proper sense of the word. The amount adsorbed depends, not on the mass of the 

 adsorbent, but on its state of subdivision, or its shape. 



The constituents of living cells consist largely of substances in the colloidal 

 state, so that it is not surprising to find that adsorption compounds are frequently 

 to be met with amongst those extracted from these cells. Specially interesting 

 are those in which lecithin is one of the components. When yolk of egg is 

 extracted with ether, a compound of lecithin with vitellin goes into solution, 

 although vitellin alone is insoluble in ether. Jecorin, again, a complex of glucose 

 with lecithin and albumin, also appears to be an adsorption compound. It has 

 been prepared by A. Mayer and Terroine (1907) by mixing solutions of acid 

 albumin, lecithin and glucose all in dilute alcohol. The mixture is evaporated 

 to dryness, extracted with ether, and precipitated from solution by absolute 

 alcohol, just in the same way as Drechsel's original preparation from the liver. 

 The other properties of this artificial jecorin are exactly those of the natural 

 one. The fact that shows it to be an adsorption compound is that its composition 

 varies with the relative proportion of the constituents of the mixture from which 

 it is made. It has been claimed that jecorin can, by repeated precipitation and 

 redissolving, be obtained of constant composition. It must be remembered, how- 

 ever, that this fact does not exclude adsorption. For one thing, if the whole 

 of the constituents are precipitated by absolute alcohol, it is obvious that the 

 precipitate will always have the same composition. Suppose further that we 

 take electro-negative paper and allow it to adsorb night-blue, which is electro- 

 positive. We find that, even from a moderately concentrated solution of the 

 dye, practically the whole is taken up; so little is left that it would escape 

 detection by analysis. Suppose that we dissolve this stained paper and re- 

 precipitate it; in the second precipitation, practically the whole of the dye 

 would go down again with the precipitate. 



Another instructive case is the artificial laccase (an oxidising enzyme) prepared 

 by Dony-H^nault (1908) by alcoholic precipitation of a solution containing gum 

 arabic, manganese formate, and sodium bicarbonate. This precipitate can be 

 redissolved in water and reprecipitated by alcohol. It is undoubtedly an 

 adsorption compound of gum with colloidal manganese hydroxide. When the 



