744 TRANSACTIONS OF SECTION I. 



enabled us to understand a little more clearly the causation 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 

 standpoint. It seemed to me then, and it appears 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 accomplish 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 investigators in this line instead of only a very 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, meagre, but they show 

 distinctly indeed that the inorganic salts are not diffused uniformly throughout 

 the cell ; that in vegetable cells they are rigidly localised, while in animal cells, 

 except those devoted to absorption and excretion, they are confined to specified 

 areas in the cell. Their localisation, 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 ex- 

 planation for the remarkable distribution, for example, of potash ealts in 

 vegetable cells. We know that, except in the chloroplatinate of potaesium and 

 in the hexanitrite of potassium, sodium and cobalt, potassium salts form no pre- 

 cipitates; and yet, in the cytoplasm of vegetable cells, the potassium is so 

 localised at a few points as to appear at first as if it were in the form of a pre- 

 cipitate. In normal active cells of Spirogyra it is massed along the edge of the 

 chromotophor, while in the mesophyllic cells of leaves it is condensed in masses 

 of the cytoplasm, which are by no means conspicuous in ordinary preparations 

 of these cells. 



This effect of surface tension in localising the distribution of inorganic salts 

 at points in the cytoplasm would explain the distribution 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- 

 moecium) it is in very intimate association with the basal elements of the cilia in 

 the ectosarc. This, indeed, would seem to indicate that the distribution of the 

 potassium is closely associated with contraction, and, therefore, with the pro- 

 duction of energy in contractile tissues. The condensation of potassium at a 

 point may, of course, be a result of a combination with portions of the cytoplasm, 

 but we have no knowledge of the occurrence of such compounds ; and, further, 

 the presence of such does not explain anything, or account for the liberation of 

 energy in motor contraction. On the other hand, the action of surface tension 

 would explain not only the localisation of the potassium but also the liberation 

 of the energy. 



In vessels holding fluids the latter, in relation to surface tension, have 

 two surfaces — one free, in contact with the air, and known as the air-water sur- 

 face ; the other, that in contact with the wall of the containing vessel (glass). In 

 the latter the tension is lower than in the former. When an inorganic com- 

 pound — a salt, for example — is dissolved in the fluid it increases the tension at 

 the air-water surface, but its dilution is much greater here than in any other 

 part of the fluid ; while at the other surface its concentration is greatest. In 

 the latter case the condition is of the nature of adsorption. The condensation on 

 that portion of the surface where the tension is least is responsible for what we 

 find when a solution of a coloured salt, as, e.g., potassium permanganate, is 

 driven through a layer of dry sand. If the latter is of some considerable thick- 

 ness the fluid as it passes out is colourless. The air-solution surface tension is 

 higher than the tension of each of the solution-sand surfaces on which, therefore, 

 the permanganate condenses or is adsorbed. The same phenomenon is observed 

 when a long strip of filter-paper is allowed to hang with its lower end in contact 

 with a moderately dilute solution of a copper salt. The solution is imbibed by 

 the filter paper, and it ascends a certain distance in a couple of minutes, when 

 if may be found that the uppermost portion of the moist area is free from even 

 a trace of copper salt. 



