302 Fischer's Theory of Edema [Dec. 



Some of Fischer's " concluding remarks.'* At the conclusion 

 of his disciission, Fischer makes the following special allusions, 

 among others, to the work of previous observers: 



There is no difficuky in understanding why Cohnheim's experi- 

 nients, in which he combined the infusion of sodium chloride Solution 

 with moderate injury to a part, always led to the development of an 

 edema more promptly than the infusion alone. The moderate injury 

 (heat, sunburn, iodine application) simply brought about, by indirect 

 means, the so necessary change in the colloids of the tissues, and the 

 increased affinity for water once being established the water of the 

 sodium chloride infusion quickly satisfied it. (Page 206.) 



The interpretation of another experimental Observation of Cohn- 

 heim^^ seems to me to need revision. Cohnheim found that an animal 

 which has been bled repeatedly, and injected after each bleeding with 

 a sodium chloride Solution, finally develops a general edema, and inter- 

 preted this as an edema of cachexia, caused through an increased per- 

 meability of the bloodvessel walls, determined primarily through a 

 hydremia. Would it not be a simpler interpretation to say that through 

 these frequent bleedings the animal becomes anemic — that is to say, 

 his Organs get into a State of lack of oxygen — and when a supply of 

 water is furnished the tissues, whether through a sodium chloride infu- 

 sion or in any other way, they simply take this up? (Page 206.) 



We need not further discuss the inadequacy of the blood pressure 

 theory to account for edema. While Cohnheim regarded blood pres- 

 sure as one of the two great factors concerned in the production of 

 edema, he also recognized that severe edemas occur in animals when 

 no change whatsoever in blood pressure is apparent. To account for 

 an edema under such circumstances he had recourse to an " increased 

 permeability of the bloodvessel walls." If in the light of our modern 

 physico-chemical conceptions we try to say just what is meant by this, 

 we have to define the bloodvessel wall as a colloidal membrane. From 

 physico-chemical observations we know that the permeability of such 

 colloidal membranes is alterable, so this far Cohnheim is on safe 

 ground. But of what consequence would an increased permeability of 

 the bloodvessels be from a pathological Standpoint? To force liquids 

 through the bloodvessel walls is not to force them into the tissues. 

 And the fluid of an edematous tissue is very decidedly in the cells them- 

 selves. Cohnheim's hypothesis would simply squeeze the edema fluid 



"Cohnheim: Allgemeine Pathologie, Zweite Auflage, Berlin, 1882, i, p. 498. 



