These agents are probably supplied by the cells of other organs.
It is quite probable that, at present, being too much concerned with the phenomena of structural chemistry, we observe the processes in the cell from a too one-sided point of view, and think too little of the physical state of the cell. We know that many reactions depend entirely upon the conditions present, if the action is to take place. For instance, a change in the reaction of the medium is sufficient to annihilate the activity of n ferment. The addition of the least trace of an electrolyte will, under certain circumstances, accelerate certain reactions; and alterations in the conditions may even upset a reaction entirely, and lead to totally different end products. The processes in the interior of the cells are surely subjected to a much greater extent to the influences of the physical state of the cell. Colloidal substances and electrolytes—the ions—and perhaps the rest of the substances in solution, certainly play a considerable rôle in their reciprocal relations. Here we meet with regulations of a kind which we are at present unable to discern. Might it not be in this direction that the collaborations of different body cells would appear of the greatest significance? Many a process, which manifests itself and attracts our attention most strongly on account of the ease with which it can be demonstrated, may perhaps be of quite a secondary
