PROCEEDINGS OF SECTION D. 495 



hydrogen atoms by three nitro groups, with the formation of picric acid, 

 has its acid properties greatly increased, and as ammonia and phosphine 

 have their basic properties greatly increased by the substitution of methyl 

 or ethyl groups for one or more of their hydrogen atoms, so ^ve should 

 expect the ion-proteid compounds, composed, as we may suppose them 

 to be, of a comparatively inert protean moiety in combination with a 

 chemically active moiety, to exhibit more or less basic or acid properties, 

 according to the basicity or acidity of the chemically active constituent, 

 or, in other words, of the ion in the surrounding medium which has the 

 higher velocity of migration. Accordingly, I found (39) that tissues 

 placed in solutions in which the anion has the higher velocity of migra- 

 tion combine readily with basic dyes, and show but a feeble affinity for 

 acid dyes; while, on the other hand, tissues placed in solutions in which 

 the cation has the higher velocity of migration combine readily with acid 

 dyes and show but slight affinity for basic dyes. 



The experiments wei-e conducted as follows: — Two species of 

 infusoria — Paramoecium and Colpodium — were thoroughly snaked in the 

 solution of the salt to be investigated by shaking them up in the 

 solution, centrifugalising and shaking up again, and so on, 10 minutes 

 being allowed between each centrifugalisation, and the process being 

 repeated three times. The infusoria were then stained in methyl green, 

 as an example of the basic dye, or in iodine-eosin, as an example of an 

 acid dye, precautions being taken in both cases to prevent reaction 

 changes in the tissue during fixation, and to exclude the possibility of 

 mere physical staining, due to the retention in the tissue by imbibition, 

 of the free color acid or color base. The results, for a detailed account 

 of which I must refer to my original paper, were strikingly in accord 

 with the hypothesis. Indeed, in solutions of potassium acetate and 

 sodium butyrate, in which the cations have very much higher migration 

 velocities than the anions, and in which, therefore, according to the 

 hypothesis which I have outlined, tissues should possess basic characters, 

 even the nuclei of infusoria failed entirely to stain in methyl green. Now 

 the nucleus of a cell is usually pronouncedly acid in its properties, and 

 methyl green, being a basic dye, is a well-known nuclear stain. The 

 effect, therefore, of solutions of these salts upon the acid and basic pro- 

 perties of tissues immersed in them must be very considerable. The 

 effects were not due to the reactions of the solutions of salts themselves, 

 because the excess of salt was always carefully removed by washing 

 before the stain was applied, and because a totally different set of results 

 was obtained if this washing was omitted. Nor were the results due to 

 alterations in the permeability of the cells for the dyes employed, for just 

 those cells, for example, which stained most intensely in methyl green 

 also stained most faintly in iodine-eosin. In other words, were we to 

 attribute these results to alterations in permeability we would have to 

 suppose that just those solutions Avhich render infusoria most permeable 

 to methyl green render them at the same time least permeable to iodine- 

 eosin, a supposition which does not fit in with any of our pi-esent know- 

 ledge of the properties of semi-permeable membranes. 



The only marked exceptions which were found to the rule that cells 

 in solutions of single salts assume the acid or basic properties of that ion 

 in the solution in which they are bathed, which has the higher migratory 

 velocity, were the cases in which the cells had been immersed in solu- 



