NEPHRITIC EDEMA 349 



supply. But Fischer liolds tluit tl)c retluction in oxidation acts chiefly 

 by increased production of acids, which greatly increase the affinity 

 of the tissue colloids for water and at the same time alter the colloidal 

 state of the capillary endothelium so that the capillaries ijecome more 

 permeable. Finally, there is probably more or less obstruction to 

 lymphatic outflow because of the increased pressure on the lymphacic 

 channels, and perhaps, also, in the case of cardiac incompetence, ob- 

 struction to the discharge of lymph from the thoracic duct into the 

 subchu'ian vein against the high intravenous pressure. 



Renal Edema. — We must recognize under this heading two dif- 

 ferent types of edema. ■ In acute nephritis (e. g., in scarlatina) toxic 

 materials appear to be the chief cause, and, as Senator contends, in- 

 jure alike the capillaries of the renal glomerules and of the subcu- 

 taneous tissues; in each case there results an increased permeability 

 which is manifested by albuminuria as a result of the injury to the 

 renal capillaries, and by edema as a result of the injury to the tissue 

 capillaries. This sort of edema is allied to that produced by peptone 

 and similar 13'mphagogues, and we might well imagine that the mech- 

 anism consisted merely in an injur}- to the capillaries through which 

 excessive fluid is driven by the blood pressure, were it not for such 

 observations as those of ]\Iendel and Hooker,^*' who found that post- 

 mortem flow is increased b}- these h'mphagogues also. We can 

 hardly account for the force exhibited in postmortem lymph flow on 

 any other ground than that it is furnished by osmotic pressure or 

 colloidal absorption unless we wish to fall back upon "vital activity" 

 of the surviving cells. Hence it is probable that even in the edemas 

 of toxic conditions, such as acute nephritis, physico-chemical factors 

 play a part, the responsible substances probabl}'' being abnormal or 

 excessive metabolic products of the cells affected by the poisons. An 

 interesting observation made by Bence" is that nephrectomized rabbits 

 develop an edema even when they are given no water at all; this would 

 seem to indicate an increased affinity of the tissues for water when 

 the renal functions are deficient. Hydremia is always a favoring 

 factor, however, and probably important in nephritic edema, ^* while 

 nearly all students of acute experimental nephritis find evidence that 

 the resulting edema depends very much upon the changes in the vessel- 

 walls.39 



In the more common edema of chronic nephritis we have to con- 

 sider, among other factors, the blood pressure. That this is not an 

 essential or even important cause, however, is shown by the fact 

 that edema is usually much, less marked in interstitial nephritis with 

 high blood pressure than it is in parenchymatous nephritis with a 



3« Amer. Jour, of Physiol., 1902 (7), 380. 

 " Zeit. f. klin. Med., 1909 (67), 69. 



38 1 earce, Arch. Int. .Med., 1909 (3), 422. 



39 See Schmidt and Schlaver, Deut. Arch. klin. Med., 1911 (104), 44; Pollak 

 Wien. kUn. Woch., 1914 (27), 98. 



