CHAPTER XIV 

 EDEMA' 



As the term edema indicates the excessive- accumulation of lymph 

 (which may be either normal or modified in composition) in the cells, 

 intercellular spaces, or serous cavities of the body, the problems of 

 edema are inseparably connected with the consideration of the proc- 

 esses of physiological formation and removal of lymph. For many 

 years the study of these processes has been a favorite field of investi- 

 gation by physiologists, and the great battle-place of the "vitalistic" 

 and ''mechanistic" schools; and to this day the forces that determine 

 the formation of lymph and its subsequent absorption have not been 

 completely understood. By the application of the principles of phys- 

 ical chemistry to the problem, however, great advances have recently 

 been made, which seem to render our understanding of both Ijanph- 

 formation and its pathological accumulation in the tissues nuicli 

 clearer and more nearly accurate than they were before. We shall 

 first consider, therefore the physiological formation of lymph, before 

 taking up the subject of edema. 



Composition of Lymph. — Lymph consists of material derived from two chief 



sources. The greater part consists of fluid passing out of the capillaries into 

 the tissue spaces; here it is modified by the addition of products of nietabolism 

 derived from the tissue-cells, and by the subtraction of materials that the cells 

 utilize in their metabolism. It is, therefore, essentially a modified blood plasma, 

 and the modifications the plasma undergoes are so slight, that, under ordinary 

 conditions, lymph shows on analysis no considerable differences from blood 

 plasma, except a relative poverty in proteins, due chifly to the impermeability 

 of the capillary walls for colloids. Its quantitative composition varies greatly^ 

 depending upon the conditions under which it is collected, whether during activitja 

 or rest, etc. The following tables of analyses have been collected by Hammarsten: 



12 3 4 



Water 939.9 934.8 957.6 955.4 



Solids 60.1 65.2 42.4 44.6 



Fibrin 0.5 0.6 0.4 2.2 



Albumin 42.7 42.8 34.7 1 



Fat, Cholesterol, Lecithin 3.8 9.2 [ 35.0 



Extractive bodies 5.7 4.4 I 



Salts 7.3 S.2 7.2 7.5 



1 and 2 are analyses of lymph from the thigh of a woman, 3 is from the contents 



of sac-like dilated vessels of the spermatic cord, 4 is lymph from the neck of a colt. 



' A complete bibliography is given by Meltzor, .\merican Medicine, 1001 (S), 

 19 cl sctj.; also by Klemensiewicz, in Krelil ami Marchaml's ll;iiull)uch d. allg. 

 Path., 1912, II (i), 311; Magnus, llandbuch d. Hiochem., 1908, 11 {2), 99; C.er- 

 hartz, ihifl., j). 116. 



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