July 28, 1911] 



SCIENCE 



101 



freezing of potatoes. Potatoes contain a 

 mechanism for converting starch into 

 sugar. Ordinarily this mechanism is con- 

 trolled by and coordinated with other 

 mechanisms. Freezing disturbs this bal- 

 ance. The mechanism for the hydrolysis 

 of starch runs riot and the potato becomes 

 sweet. Another instance is the coloration 

 of the leaves in the autumn. Leaves contain 

 among other things chlorophyll, chromo- 

 gens and an oxidation mechanism. Under 

 ordinary conditions this mechanism is 

 held in check. Frost, however, plasmolyzes 

 the cells, intermixes the protoplasm, and 

 the oxidations run riot. Chlorophyll is 

 bleached so that yellow pigments, such as 

 carotin and xanthophyll, which are ordi- 

 narily masked by the green, become evi- 

 dent, while other substances, either pre- 

 existent or formed during plasmolysis, are 

 converted into the brilliant pigments of 

 our autumn woods. 



Now ever since the processes of life have 

 been studied at all chemically, the ease and 

 efficiency with which protoplasm brings 

 about reactions has filled the chemist with 

 awe. Reactions which he is able to per- 

 form in vitro only with difficulty by the 

 use of powerful agents and high tempera- 

 tures, protoplasm brings about perfectly 

 at low temperatures. If we pursue our 

 conception of protoplasm as a hetero- 

 geneous system further we can imagine 

 mechanisms by which such action is con- 

 ceivable. 



Many reactions go on rapidly in proto- 

 plasm to a high degree of completeness, 

 while in vitro the rate may be slow and 

 the yield insignificant. This becomes in- 

 telligible in a heterogeneous medium with- 

 out necessarily resorting each time to the 

 action of an enzyme. We have only to as- 

 sume that the reaction takes place in one 

 phase and that one or more of the products 

 disappear into another phase as fast as 



formed. In this way reactions might go 

 on at a rate and to an equilibrium quite 

 different from those in vitro, for the prod- 

 ucts of the reaction would be removed from 

 the seat of reaction almost as fast as 

 formed. Such a mechanism might be 

 merely the result of different solubility in 

 the phases. 



A similar line of thought throws light 

 upon the fact that a substance present in 

 protoplasm as a whole, in such minute con- 

 centration that a priori its influence ought 

 to be negligible, may nevertheless exert a 

 profound effect. We need not necessarily 

 assume that this apparently disproportion- 

 ate effect is produced by a catalytic mech- 

 anism. In a heterogeneous system the 

 concentration of a given constituent as de- 

 termined by quantitative analysis of the 

 whole may be a spurious value, because 

 this constituent may not be evenly dis- 

 tributed throughout the heterogeneous 

 system. It may be almost absent in one 

 phase and concentrated nearly entirely in 

 another, and this difference in distribution 

 may also be merely the result of difference 

 in soliibilities. Hence in protoplasm sub- 

 stances may be concentrated greatly in defi- 

 nite localities and thus make reactions pos- 

 sible which at low concentrations would be 

 infinitely slow. 



An uneven distribution of the various 

 constituents of protoplasm such as this, is 

 not the only way in which the concentra- 

 tion may vary according to this multiple 

 phase hypothesis of protoplasmic structure. 

 Even in the same phase the concentration 

 of the substances in that phase may be 

 caused to vary greatly by the energy at 

 work in surfaces. It is a well-known fact 

 that substances which diminish surface ten- 

 sion or the tendency inherent in liquids to 

 assume that shape which reduces the sur* 

 face to a minimum, accumulate at the sur- 

 face so that they are present in the thin 



