Influence of Acids in the Production of Edema. 107 
brought about either through their abnormal production, or through the inadequate 
removal of such as some consider normally produced in the tissues, is chiefly responsi- 
ble for this increase in the affinity of the colloids for water, though the possibility of 
explaining at least some of the increased affinity for water through the production or 
accumulation of substances which affect the colloids in a way similar to acids or through 
the conversion of colloids having but little affinity for water into such as have a greater 
affinity must also be borne in mind." 1 
Fischer's views on the influence of acid in the production of 
pathological edemas appear to us to be over-emphasized. Special 
stress was laid by Fischer upon lactic acid as a causative factor in 
pathological edema, but apparently no experiments were per- 
formed with that acid. The action of electrolytes on the power 
of lactic acid to excite water absorption by colloids was not 
ascertained. Acids such as hydrochloric were Fischer's chief 
reliance in his experiments with acids. 
We find, when moist shreds of fibrin are severally suspended in 
gelatin solution, peptone solution, fresh egg white, blood, milk, and 
meat juice, that hydrochloric acid solution (0.2 per cent, to 10 per 
cent.) may be added to the mixture in each case in any proportion 
without inducing visible effects on the fibrin shreds, unless sufficient 
acid is added to provide an excess in the free state. Very large quan- 
tities of acid may be added to such mixtures without appreciable 
bloating effect. 2 If the colloids in the artificial solutions and proto- 
plasmic liquids enumerated above are combined with any propor- 
tion of the acid up to exactly their maximum affinity for it (hy- 
drochloric acid), so that the liquids while strongly acid to litmus 
respond negatively to tests for free acid, then moist fibrin shreds 
can be kept in such acid fluids indefinitely without swelling to any 
perceptible degree. Warm concentrated gelatin solutions may 
be put into these conditions of free and combined acidity. After 
such solutions have been permitted to gelatinize, moist fibrin 
shreds which have been imbedded in the resultant jellies swell 
perceptibly, provided the gelatinized mass contains free acid, but 
the shreds do not appear to absorb water from the medium if its 
contained acid is only in combined form. It is obvious that such 
special emphasis is laid by us on the part of the quotation which we have 
italicized. 
2 Similar observations have been made with alkaline mixtures. We expect to 
describe, in the near future, a new test for free alkali based upon the behavior of 
fibrin in association with dissolved protein in alkaline media. 
