EDEMA 179 



PART IV 



Lymph Production and Edema from the 

 Physico-Chemical Standpoint 



The Production of Lymph. For a complete discussion of the physi- 

 ology of lymph production the reader is referred to the numerous refer- 

 ences on the subject. In the present discussion it will be possible to con- 

 sider lymph production only from the physico-chemical viewpoint. It' 

 may, however, be stated, as originally pointed* out by Asher(a) (&) and 

 since confirmed by many other authors, that a striking fact with relation to 

 the normal production of lymph is that the rate of lymph production and 

 flow depends on tissue activity. It cannot be said that increased lymph 

 production, even under normal circumstances, cannot occur without in- 

 creased tissue activity, but. the evidence seems conclusive that increased 

 tissue activity is always accompanied by an increased rate of formation 

 and flow of lymph. 



The theories of lymph production may be divided into two classes: 

 first, those which assume a specific secretory activity on the part of the 

 endothelial cell lining the capillaries ; and second, those which attempt to 

 explain the process by applying the principles of physics and of physical 

 chemistry. Knowledge of the physico-chemical factors entering into the 

 process of lymph formation is so lacking in detail that judgment as to the 

 necessity for postulating a specific secretory activity is rendered difficult. 

 In any case, a secretory theory would not dispense with the necessity of 

 considering the physico-chemical factors involved, for only through them, 

 or together with them, can a specific secretory power on the part of the 

 cells be effective. 



It is customary to consider the mechanism of lymph formation, flow, 

 and reabsorption separately. These are, however, all associated in the 

 same process, and cannot be independent phenomena. From the point of 

 view of the forces concerned, the subject may be considered from two 

 standpoints: first, that of the fluid which enters the lymphatic circula- 

 tion' from the tissues ; and second, that which is returned from the tissues 

 to the capillaries. 



The conditions which determine one or the other disposition of lymph 

 resemble the conditions concerned in the flow of water or the flow of elec- 

 tricity. There must first be a source of the substance which is to move, 

 and of energy which is to result in motion. There must also be a gradient 

 or a difference in potential between the points between which movement 

 is to occur. So long as there is movement, stable equilibrium is never 

 actually attained, but there is a correlation reached and maintained be- 

 tween the source of matter and energy, the gradient and the flow, whether 



