174 FRANKLIN C. McLEAN 



cells in cases of heart failure of long standing. Polycythemia in these 

 cases is assumed to result from diminished oxygen supply to the tissues, 

 analogous to polycythemia produced by living at high altitudes. 



Summary. The changes observed in the blood of patients with heart 

 failure seem to be more concerned with the failure of the lungs com- 

 pletely to oxygenate the blood and to withdraw carbon dioxid from it^ 

 than with the failure of the kidneys to carry on their excretory function., 

 The tissues also contribute to the changes in venous blood, partly on ac- 

 count of the increased time during which the blood is in contact with the 

 tissues, and possibly on account of chemical changes in the tissues 

 themselves. 



Renal Excretory Function in Its Relation to Edema. The demonstra- 

 tion by Bright of albuminuria and pathological changes in the kidneys 

 in cases of edema, and the readily observed discrepancy between fluid 

 intake and fluid output in these cases, to which attention was directed 

 by Stewart and by Bartels, have led to the assumption, held for a 

 long time, that edema is due to the failure of the kidneys to excrete water. 

 Later Koranyi drew attention to the retention of the products of protein 

 metabolism by the kidneys, and ascribed edema to a consequent increase 

 in the osmotic pressure in the tissues, with resulting retention of water. 

 Widal and, at about the same time, Strauss(d), showed that the amount of 

 sodium chlorid in the diet greatly influenced the occurrence and persistence 

 of edema, and assumed that this was due to retention of salt by the kid- 

 neys, with consequent increase in osmotic pressure in the tissues. 



Pearce(fr) studied the relative etiological importance of renal injury, 

 vascular injury and hydremic plethora in the production of edema, and 

 concluded that for the production of general edema all three factors' are 

 essential, no one of them, and no combination of two, being sufficient. 



McClure found that when the ureters of the toad, Anura, were ligated, 

 and the animal placed in water, generalized edema occurred in a short 

 time, and concluded that edema in this case was due to the blocking of 

 urinary excretion. Swingle similarly removed the pronephros of the 

 larval form of Anura and found that when the operation was performed 

 after the pronephros had become functionally active, edema followed the 

 operation and frequently resulted in the bursting of the larva. It is worthy 

 of note, however, that total anuria in man, or under experimental con- 

 ditions in warm-blooded animals, almost never leads to edema, in spite 

 of profound changes in the chemical and physico-chemical characteristics 

 of the blood and tissue fluids. 



In certain diseases, however, notably diffuse nephritis and heart 

 failure, evidences of renal insufficiency are coincident with edema, and 

 since the time of Stewart and of Bartels a causal relation between the two 

 has been regarded as probable. But it should be remembered that a 



