454 



SCIENCE 



[N. S. Vol. XXXII. No. 823 



The objections whicli I now urge against 

 the conclusions drawn from the results of 

 digestion experiments have developed out 

 of my own observations on j^east cells, 

 diatoms, Spirogyra, and especially the 

 blue-green algse. The latter are, as is 

 Spirogyra, encased in a membrane which 

 is an effective barrier to all colloids. When, 

 therefore, threads of Oscillaria are sub- 

 jected to the action of artificial gastric 

 juice, a certain diminution in volume is ob- 

 served owing to the dissolving power of the 

 hydrochloric acid, and an alteration of the 

 staining power of certain structures is 

 found to obtain, but the pepsin has nothing 

 to do with these, as may be determined by 

 examination of control preparations 

 treated with a solution of hydrochloric acid 

 alone. 



It is thus seen how slender is our knowl- 

 edge of the chemistry of cells derived from 

 staining methods and from digestion ex- 

 periments. That, however, has not been 

 the worst result of our confidence in our 

 methods. It has led cytologists to rely on 

 these methods alone, to leave undeveloped 

 others which might have thrown great 

 light on the chemical constitution of the 

 cell, and which might have enabled us to 

 understand a little more clearly the causa- 

 tion of some of the vital phenomena. 



It was the futility of some of the old 

 methods that led me, twenty years ago, to 

 attack the chemistry of the cell from what 

 appeared to me a correctly chemical stand- 

 point. It seemed to me then, and it ap- 

 pears as true now, that a diligent search 

 for decisive chemical reactions would yield 

 results of the very greatest importance. 

 In the interval I have been able to accom- 

 plish only a small fraction of what I hoped 

 to do, but I think the results have justified 

 the view that, if there had been many in- 

 vestigators in this line instead of only a few, 

 the science of cytochemistry would play a 



larger part in the solution of the problems 

 of cell physiology than it now does. 



The methods and the results are, as I 

 have said, meager, but they show distinctly 

 indeed that the inorganic salts are not dif- 

 fused uniformly throughout the cell; that 

 in vegetable cells they are rigidly localized, 

 while in animal cells, except those devoted 

 to absorption and excretion, they are con- 

 fined to specified areas in the cell. Their 

 localization, except in the case of inorganic 

 salts of iron, is not due to the formation of 

 precipitates, but rather to a condition 

 which is the result of the action of surface 

 tension. This seems to me to be the only 

 explanation for the remarkable distribu- 

 tion, for example, of potash salts in veg- 

 etable cells. We know that, except in the 

 chloroplatinate of potassium and in the 

 hexanitrite of potassiiim, sodium and co- 

 balt, potassium salts form no precipitates j 

 and yet, in the cytoplasm of vegetable cells, 

 the potassium is so localized at a few points 

 as to appear at first as if it were in the 

 form of a precipitate. In normal active 

 cells of Spirogyra it is massed along the 

 edge of the chromotophor, while in the 

 mesophyUic cells of leaves it is condensed 

 in masses of the cj^toplasm, which are by 

 no means conspicuous in ordinary prepara- 

 tions of these cells. 



This effect of surface tension in localizing 

 the distribution of inorganic salts at points 

 in the cytoplasm would explain the distri- 

 bution of potassium in motor structures. 

 In striated muscle the element is abundant 

 in amount, and is confined to the dim bands 

 in the normal conditions. In Vorticella, 

 apart from a minute quantity present at a 

 point in the cytoplasm, it is found in very 

 noticeable amounts in the contractile stalk;- 

 while in the holotrichate infusoria {Para- 

 mcecium) it is in very intimate association 

 with the basal elements of the cilia in the 

 ectosare. This, indeed, would seem to indi- 



