PROCEEDINGS OF SECTION D. 497 



water. If, now, to the highly toxic solution of sodium chloride in the con- 

 centration in which it occurs in sea water there be added the even more 

 toxic combination of the other remaining salts in sea water in the con- 

 centrations in which they occur therein, we obtain a solution in which 

 Gammarns lives as long as it does in sea water — that is, as far as our pur- 

 poses are concerned, indefinitely. 



If the action of salts were a simply osmotic one the relation of con- 

 centration to toxicity should be simply a linear one. Wolgang Ostwald, 

 however, working with fresh-watei Gammarus, found a sudden and 

 extraordinary increase in toxicity at a critical concentration of all the 

 solutions, the eftects of which he investigated, and this sudden increase 

 in toxicity did not by any means occur at the same osmotic pressure in 

 different solutions. 



Osterhout, working with a fresh-water alga fVaucheria sessilisj, 

 found that it lived three or four weeks in distilled water, and indefinitely 

 in a dilute sea water corresponding in osmotic pressure to about a -3V 

 molecular sodium chloride ; but it was killed in a few ramates in pure 

 3-3 molecular sodium chloride, and in a few days by ten thousandth 

 molecular sodium chloride. Very numerous similar and equally striking 

 experiments of Osterhout's, an account of which will be found in the 

 papers to which I have alluded, all point to similar conclusions. Indeed 

 the whole series of expei'iments upon antagonistic salt effects and physio- 

 logically balanced solutions (44) establish beyond doubt the very subordi- 

 nate role played by osmotic pressure in phenomena of toxicity. 



Turning, therefore, to the other chemical and physico-chemical 

 factors which may be concerned, we are naturally led, in the first place, 

 to consider the influence of concentration upon the nature and propor- 

 tions of the ion-proteids formed in the tissues. Were the reaction 

 between an ion of a salt and the proteins in a tissue phenomena analo- 

 gous to the neutralisation of a simple base or acid by another acid or 

 base, and were the toxic action of a salt mainly due to the nature and 

 proportion of the ion-proteid formed in the tissue, we should expect to 

 find, as in the curves representing the neutralisation of an acid by a base 

 (45), a comparatively slow initial rise in toxicity as the concentration of 

 I the toxic substance increased, followed by a relatively rapid rise in toxi- 

 'city to a limit representing the extreme toxicity which it is possible to 

 obtain at any concentration of the toxic substance. Accurate investi- 

 gations on the influence of a series of concentrations upon toxicity are 

 very few and are much to be desired. The experiments of Wolfgang 

 Oswald, however, to which I have alluded, tend to support the idea that 

 toxicity depends upon a process analogous to the neutralisation of a 

 simple acid by a simple base, or vice versa. Certain other experiments 

 upon tissues, however, show that this simple view of the case is inadmis- 

 sible. In experiments on the influence of the concentration of sodium 

 chloride solutions upon the amount of water absorbed by a frog's muscle 

 placed in the solution. Loeb (46) found that in dilute solutions, in a given 

 time, the muscle absorbs a large quantity of water; then, as the concen- 

 tration is increased, the amount of water absorbed by the muscle reaches 

 a minimum, very nearly zero : then, as the concentration is still further 

 increased, the amount of water taken up by the muscle gradually increases 

 f- also until it reaches a second maximum. Obviously this in no way cor- 

 l2 



