FACTORS CONCERNED IN LYMPH FORMATION 465 



same as the maximum in the blood, this fact loses its weight as 

 an argument in favour of the nitration hypothesis when we re- 

 member that, according to Asher, all the solids of the lymph are 

 markedly increased when even small quantities of crystalloids are 

 injected into the veins. Upon the whole, then, it may be con- 

 cluded that up to the present it has not been shown that filtration 

 due to the excess of pressure in the capillaries over that in the 

 lymph spaces is an effective factor in the formation of lymph. Nor 

 is it at all easier to explain lymph formation as a matter of pure 

 osmosis or diffusion. Lazarus-Barlow found, for example, that in 

 the great majority of his experiments the injection of a concen- 

 trated solution of sodium chloride, dextrose or urea into a vein was 

 followed, not by an initial diminution in the outflow of lymph (as 

 might have been expected if the exchange of water between the 

 blood and the tissue spaces, and between the tissue spaces and the 

 lymph capillaries, was regulated solely by differences in osmotic 

 pressure), but by an immediate increase. And Carlson has shown 

 that the osmotic pressure of lymph coming from the active salivary 

 glands, as measured by the freezing-point method, may, under 

 chloroform or ether anaesthesia, be distinctly less than that of the 

 blood-serum. Water must therefore be passing from a liquid of 

 higher to one of lower osmotic concentration. 



Nevertheless, it would be erroneous to assume that because 

 osmosis and diffusion have not been shown to satisfactorily account 

 for all the phenomena of lymph formation, they exert no influence 

 upon it. It is probable, indeed, that their action is fully as im- 

 portant as in absorption from the alimentary canal, although, as in 

 absorption, it is often overlaid and always modified by the specific 

 permeability of the blood-capillary walls, the lymph-capillary walls, 

 and the tissue cells in general, in virtue of which they exert an 

 action upon the quantity and composition of the lymph analogous 

 to the action exerted in a higher degree by the cells of the digestive 

 glands upon the quantity and composition of the liquids passing 

 into their ducts. 



It is not difficult to illustrate the fact that phenomena of osmosis and 

 diffusion emerge, although not of course in such purity as in physical 

 experiments, when we study the interchange between the blood and 

 the tissue liquids. If, for example, a hypertonic solution of sodium 

 chloride is injected into the blood, water rapidly passes from the tissues 

 to the blood as it would through a semipermeable membrane, and the 

 blood becomes diluted. At the same time sodium chloride leaves the 

 blood and passes into the tissues, as it would do by diffusion from a 

 place of higher to a place of lower concentration. But after this has 

 gone on for some time, and the concentration of the blood in salt has 

 sunk, it may be, to that in the lymph, salt still continues to pass out 

 of the blood, and the excess of water also leaves the bloodvessels till the 

 osmotic pressure of the blood has again become normal. When isotonic 

 and even hypotonic solutions of sodium chloride are injected, salt also 



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