INFLUENCE OP NERVES ON LYMPH FORMATION 473 



secretin at all, but to lymphagogue substances, including proteose, 

 extracted with the secretin from the intestinal mucous membrane. 

 A solution of secretin can be prepared which causes a considerable 

 increase in the secretion of pancreatic juice and bile, but no augmen- 

 tation whatever in the flow of lymph from the thoracic duct. 

 Again, it was asserted that peptone, a noted lymphagogue, produces 

 a great increase in the biliary secretion. It has been demonstrated, 

 however, that the action of the peptone is merely to cause expul- 

 sion of the contents of the gall-bladder by the mechanical effect of 

 the swelling of the liver, and not at all to stimulate the liver-cells 

 to form more bile. For it produces no effect on the flow of bile 

 if the gall-bladder be emptied or the cystic duct tied before the 

 injection (Ellinger). That active salivary secretion is not accom- 

 panied by increased lymph-flow from the lymphatics of the salivary 

 glands has been mentioned above. Nevertheless, we may safely 

 assume that the activity of the organs does make a contribution to 

 the lymph to its solids, if not in any important degree to its water- 

 content, although to say that they alone are concerned in its forma- 

 tion, to the exclusion of the capillaries, is altogether an over-state- 

 ment. The waste-products of the tissues pass into the lymph, and 

 possibly, as Koranyi suggests, may, by increasing its molecular 

 concentration, cause the passage of some water into it from the 

 blood. Or the decomposition of the large protein molecules, which 

 in tissue metabolism are breaking down into numerous smaller 

 molecules, may entail an increase of osmotic pressure in the cells 

 themselves, which in turn may lead to withdrawal of water by the 

 cells from the tissue liquid. The osmotic pressure of the liquid 

 may thus rise, and water may pass into the tissue spaces from the 

 blood. The molecular concentration of lymph (except in anaesthe- 

 tized animals as mentioned above) is in general somewhat greater 

 than that of blood- serum e.g., in one observation A of serum 

 was 0-605 C., and of lymph 0-610 C. For the solid tissues, the 

 freezing-point of which, however, cannot be as satisfactorily deter- 

 mined as that of liquids, the following values of A were obtained : 

 Brain, 0-65; muscle, 0-68; kidney, 0-94; liver, 0-97; while for 

 blood it was 0-57 (Sabbatani). 



To sum up, we may say that while the physical processes of filtra- 

 tion, osmosis and diffusion may play a part in the passage of water 

 and solids through the walls of the blood capillaries, as well as from 

 the tissue-cells into the tissue spaces, and from these spaces into the 

 lymph capillaries, there is much which they leave unexplained, and 

 which at present, for the want of a more precise term, we must attribute 

 to secretory activity. 



Influence of Nerves on Lymph Formation. In one instance 

 it appears to have been shown that lymph may be formed 

 under the influence of secretory nerves. In the males of certain 



