ipii] William J. Gies 271 



in edema. The pathological conditions attending the development 

 of edema effect the transference of abnormally large and unwieldy 

 volumes of intravascular water to extravascular positions, or are 

 responsible for special interferences with the normal movement of 

 extravascular water into the circulation, or induce both of these 

 general results. 



The mechanical and chemical factors involved in the localiza- 

 tions of water which are characteristic of edema, have long been 

 subjects of experimental inquiry and earnest discussion. It has 

 generally been assumed that the excess of water in an edematous 

 tissue represents, in effect, an abnormal relation between lymph 

 production and lymph removal (absorption), i. e., that edema is 

 pathological lymph formation, collection, and retention. For this 

 reason practical study of the presumed causes of edema has been 

 repeatedly directed to an extension of our knowledge of, and to 

 reexaminations of the factors and influences involved in, physio- 

 logical lymph formation. In recent years, however, stress has been 

 laid upon local tissue disturbances, such as deficient intracellular 

 oxidations, as the causal influences in the development of edema. 

 (See page 279.) Such intracellular conditions would exert hydro- 

 philic influences directive of and coordinate with, hut not inde- 

 pendent of, the primary phenomena in physiological lymph pro- 

 duction. 



Lymph and its relation to edema. The foregoing Statements 

 indicate that edema, in the prevalent view, is a pathological accumu- 

 lation of lymph. Let us consider for a few minutes our general 

 knowledge of the mechanical factors in the physiological formation 

 of lymph. 



Blood circulates, under pressure, to all living parts of the body. 

 Plasma (water with substances dissolved in it) passes through the 

 thin walls of the blood capillaries into the tissue spaces and becomes 

 (mingles with) extravascular (interstitial) lymph. Under normal 

 conditions all the cells — all the " tissue elements " — are continuously 

 bathed with flowing lymph. Interstitial lymph carries oxygen, 

 water, nutrients and stimulants to the cells and, in exchange, it 

 receives the expelled products of intracellular metabolism. Inter- 

 stitial lymph (water with substances dissolved in it) passes through 



