LYMPH. 365 



theory, from the consequent rise of pressure in the capillary regions but also 

 an increased concentration in the percentage of proteid in the lymph. This 

 latter fact has been satisfactorily explained by the experiments of Starling. 1 

 According to this observer, the lymph formed in the liver is normally more 

 concentrated than that of the rest of the body. The occlusion of the vena 

 cava causes a marked rise in the capillary pressure in the liver, and most of 

 the increased lymph-flow under these circumstances comes from the liver, 

 hence the greater concentration. The results of this experiment, therefore, do 

 not antagonize the filtration-and-diffusion theory. 



3. Heidenhein discovered that extracts of various substances which he 

 designated as " lymphagogues of the first class " cause a marked increase in the 

 flow of lymph from the thoracic duct, the lymph being more concentrated than 

 normal, and the increased flow continuing for a long period. Nevertheless, 

 these substances cause little, if any, increase in general arterial pressure ; in 

 fact, if injected in sufficient quantity they produce usually a fall of arterial 

 pressure. The substances belonging to this class comprise such things as pep- 

 tone, egg-albumin, extracts of liver and intestine, and especially extracts of the 

 muscles of crabs, crayfish, mussels, and leeches. Heidenhain supposes that 

 these extracts contain an organic substance which acts as a specific stimulus to 

 the endothelial cells of the capillaries and increases their secretory action. The 

 results of the action of these substances has been differently explained by those 

 who are unwilling to believe in the secretion theory. Starling 2 finds experi- 

 mentally that the increased flow of lymph in this case, as after obstruction of 

 the vena cava, comes mainly from the liver. There is at the same time in the 

 portal area an increased pressure which may account in part for the greater flow 

 of lymph ; but, since this effect upon the portal pressure lasts but a short time, 

 while the greater flow of lymph may continue for one or two hours, it is 

 obvious that this factor alone does not suffice to explain the result of the injec- 

 tions. Starling suggests, therefore, that these extracts act pathologically 

 upon the blood-capillaries, particularly those of the liver, and render them 

 more permeable, so that a greater quantity of concentrated lymph filters 

 through them. No experimental proof is given to show that these extracts 

 do so affect the capillary walls. Starling's explanation is supported by 

 the experiments of Popoff. 3 According to this observer, if the lymyh is col- 

 lected simultaneously from the lower portions of the thoracic duct, which con- 

 veys the lymph from the abdominal organs, and from the upper part, which 

 contains the lymph from the head, neck, etc., it will be found that injection 

 of peptone increases the flow only from the abdominal organs. Popoff finds 

 also that the peptone causes a dilatation in the intestinal circulation and a 

 marked rise in the portal pressure. At the same time there is some evidence 

 of injury to the walls of the blood-vessels from the occurrence of extravasa- 

 tion in the intestine. Cohustein, 4 from experiments made with peptone solu- 



1 Journal of Physiology, 1894, vol. xvi. p. 234. 2 Ibid., 1894, vol. xvii. p. 30. 



3 CentralblaUfiir Physiologic, 1895, Bd. ix., No. 2. 



4 Archiv fur die gesammte Physiologic, 1894, Bd. lix. S. 366. 



