FORMATION OF LYMPH 



Different Kinds of Lymph. -We ought to distinguish the lymph 

 as we collect it from the great lymphatic trunks, not only from the 

 liquids of the serous cavities, but still more sharply from the liquid 

 which fills the multitudinous clefts and spaces of the tissues. It is 

 now pretty definitely established that the tissue spaces do not com- 

 municate by actual passages with the lymphatic vessels, but that 

 the latter form everywhere a closed system like the blood- vascular 

 system, the lymph capillaries merely lying in the tissue spaces 

 (Sabin, etc.). This conception entails a radical change in the 

 current views of lymph production. If the lymphatics form a 

 closed system, the lymph cannot be actual tissue fluid, but only 

 tissue fluid modified by its passage through the walls of the lymph 

 capillaries, just as tissue fluid is not actual blood-plasma, but plasma 

 modified by its passage through the walls of the blood capillaries 

 as well as by exchange with the tissue elements. 



Although it is customary to speak of the lymph obtained from 

 the lymphatic vessels as if it were perfectly homogeneous, there is 

 no experimental ground for supposing that the lymph from different 

 tracts, or the tissue liquid in contact with the cells of different 

 organs, or even the tissue liquid in contact with one and the same 

 cell at different parts of its periphery, has a uniform composition, 

 or even a uniform molecular concentration. There are, indeed, 

 certain general considerations which show that this cannot be so. 

 Still less can it be assumed that the serous cavities, although they 

 come into relation with lymphatics and bloodvessels in their walls, 

 are analogous to colossal tissue spaces or even to expansions of the 

 closed lymphatic system, or that the liquids contained in them, 

 normally in scant amount, are simply tissue, or if not tissue, then 

 simply lymphatic lymph. The cerebrospinal fluid, which bathes 

 the external surface of the central nervous system and fills its 

 cavities, and the special liquids of the eyeball the aqueous humour 

 and the liquid of the vitreous humour although no doubt, in 

 addition to their other functions, they may in some degree minister 

 to the nutrition of the tissues with which they are in contact, are 



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