350 EDEMA 



« 



much lower pressure. Toxic substances are, of course, also present in 

 the blood, and may alter capillary permeabihty; these toxic substances 

 may account for the lo-calized edemas and erythemas sometimes ob- 

 served in nephritis. But probably most important is the action of 

 the crystalloids which the kidney does not excrete, and which seem 

 to be stored up in the tissues, where they cause transudation of water 

 under the influence of their osmotic pressure. For example, Rzent- 

 kowski"*" found that the average lowering of the freezing-point by the 

 edematous fluid in nephritis was 0.583°, in cardiac dropsy it was 0.548°, 

 and in tuberculous pleuritis 0.526°. This indicates ':hat the osmotic 

 concentration of the fluid is highest in renal dropsy, and supports the 

 belief that here and in cardiac dropsy osmotic pressure plays a more 

 important part than it does in inflammatory exudation. ^^ Of the 

 crystalloids that cause accumulation of fluid in the tissues, sodium 

 chloride seems to be the most important. 



Retention of Chlorides in Edema. ^^ — From the investigations made by numer- 

 ous clinicians, especially the French, it appears that — (1) in nephritis with edema 

 a retention of sodium chloride frequently occurs; (2) that elimination of the 

 chlorides is often increased during periods of improvement of the edema; (3) 

 that a reduction of the amount of chlorides in the diet sometimes causes a great 

 improvement in the edema, while administration of chlorides may make the 

 edema much worse. There are, however, observations that also indicate that 

 chloride retention does not account for many cases of renal drops}', for com- 

 monly the above-mentioned conditions are not fulfilled." Nevertheless, it cannot 

 be denied that chloride retention is sometimes an important causative factor in 

 the edema of parenchymatous nephritis." If the retained chlorides obeyed the 

 ordinary laws of diffusion, we should expect them to become distributed alike in 

 the blood and tissues, so that they would merely cause an equal increase in the 

 fluids of the blood and of the tissues; that is to say, there would be an hydremic 

 plethora due to retention of water in the body by the accumulating chlorides. 

 But, according to a number of observers, there is a specific retention in the tissues, 

 which Strauss calls " historetention," and which explains the local edema. The 

 way in which the historetention is produced is, however, not understood, and 

 not all observers accept this hypothesis. If chlorides do bear a causative rela- 

 tion to edema, the predilection of the subcutaneous tissues for edematous accumu- 

 lations may be explained by the observation that when salt is given to an animal 

 an undue proportion (28-77 per cent.) accumulates in the skin." In many 

 conditions other than nephritis, there is also a chloride retention (e. g., pneu- 

 monia, cardiac incompetence, sepsis, typhoid), and the edemas observed in these 

 diseases may possibly depend upon chloride retention, as many French authors 



^0 Berl. klin. Woch., 1904 (41), 227. 



^1 Epstein (Amer. Jour. Med. Sci., 1917 (154), 638) calls attention to the de- 

 crease of serum proteins (sometimes GO to 70 per cent.) and ascribes the edema to 

 lowered osmotic pressure of the blood from loss of colloids. Low protein content 

 of the blood might more probably favor edema by reducing the amount of fluid 

 which the blood can hold as a hvdrophile colloid. 



'2 Literature, r6sum6 by Widal and Javal, Jour. Physiol, et Pathol, 1903 (5), 

 1107 and 1123; Rumpf, Miinch. med. Woch., 1905 (52), 393. Review in Albu 

 and Neuberg's "Mineralstoffwochsel," Berlin, 1900, pp. 171-178; Georgopulus, 

 Zeit. klin. Med., 1900 (60), 411; Christian, Boston Med. and Surg. Jour., 1908 

 (158), 416; Palmer, Arch. Int. Med., 1915 (15), 329. 



"See Blooker, Deut. Arch. klin. Med., 1909 (96), 80; Fischer, "(Edema and 

 Nephritic." 



** See Borchardt, Deut. med. Woch., 1912 (38), 1723. 



" Schade, Zeit. exp. Path. u. Ther. 1913 (14), 1. Also gives an interesting 

 discussion of the relation of the skin to euenui. 



