18G FRANKLIN C. McLEAN 



equilibrium, and although their movements in response to disturbance in 

 the acid-base equilibrium are not fully understood, it seems probable that 

 such movements may influence osmotic equilibrium, and hence the regula- 

 tion of volume. The possible sources of energy for a disturbance of 

 osmotic equilibrium in cases of nephritis are not so easily defined. There 

 is evidence of disturbance in the acid-base equilibrium, particularly in 

 acute nephritis, in the diminished content of bicarbonate in the blood, 

 supposedly due to the retention of acids by the kidneys, but so far this 

 disturbance has not been definitely related to the occurrence of edema. 



Epstein, on the basis of his chemical analyses of the serum proteins 

 in chronic parenchymatous nephritis, and on Starling's theory in regard 

 to the balance between difference of osmotic pressure and hydrostatic 

 pressure between the capillaries and tissue fluids, ascribes the occurrence 

 of edema to the loss of protein from the blood plasma, and a corresponding 

 diminution in the difference between the osmotic pressure of plasma and 

 tissue fluids, resulting in a relative increase in the osmotic pressure of 

 the tissue fluids. The evidence in favor of this theory consists entirely of 

 favorable results in a series of patients treated with high protein diet, 

 in an effort to restore to the body its lost protein. In such cases the 

 composition of the blood plasma was brought back towards normal, and 

 edema which persisted during other methods of treatment, improved or 

 disappeared. MacLean and DeWesselow, while confirming the favorable 

 effects of high protein diet in edema due to chronic parenchymatous 

 nephritis, have shown that a favorable influence may be observed without 

 any change in the protein content of the plasma. Their results seem, 

 therefore, to throw doubt on Epstein's theoretical interpretation of his 

 results. 



Hydrophilic Action of Colloids. Changes in the content of free water 

 of the tissue fluids, and hence readjustment of volume through the forces 

 just discussed, particularly hydrostatic pressure and diffusion pressure of 

 the solvent, are believed by Fischer to be responsible for the occurrence of 

 edema. Fischer's explanation of the process, though based originally on 

 the findings of Araki(c) and of Loeb, includes a consideration of factors 

 Hitherto deemed unimportant in the process. 



Fischer attributes edematous swelling in the tissues to an increased 

 inhibition of water by colloid substances, due to increased acid formation. 

 That colloid substances do swell in acid solutions is well known. Fischer, 

 however, has brought forward no quantitative evidence to show that this 

 swelling of colloids occurs, under conditions in the body, to an extent 

 sufficient to account for the phenomenon of edema. Henderson, Palmer, 

 and Newburgh have moreover shown that the extremes of acidity neces- 

 sary to cause a significant swelling of colloids, outside of the body, are 

 far beyond the range of acidity found in the body, or compatible with 

 life. Crozier has shown also, by the aid of indicators, that the range of 



