476 BLOOD AND LYMPH. 



those who are unwilling to believe in the secretion theory. Starling* 

 finds experimentally 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 

 that 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 injections. 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 flows through them. Starling's 

 explanation is supported by the experiments of Popoff.f According 

 to this observer, if the lymph is collected simultaneously from the 

 lower portion of the thoracic duct, which conveys the lymph from 

 the abdominal organs, and from the upper part, which contains the 

 lymph from the head, neck, etc., it is 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 extravasations in the intestine. As 

 far, therefore, as the action of the lymphagogues of the first class is 

 concerned, it may be said that the advocates of the filtration-and- 

 diffusion theory have suggested a plausible explanation in accord 

 with their theory. The facts emphasized by Heidenhain with 

 regard to this class of substances do not compel us to assume a 

 secretory function for the endothelial cells. 



4. Injection of certain crystalline substances such as sugar, 

 sodium chlorid and other neutral salts causes a marked increase 

 in the flow of lymph from the thoracic duct. The lymph in these 

 cases is more dilute than normal, and the blood-plasma also becomes 

 more watery, thus indicating that the increase in water comes from 

 the tissues themselves. Heidenhain designated these bodies as 

 "lymphagogues of the second class." His explanation of their 

 action is that the crystalloid materials introduced into the blood are 

 eliminated by the secretory activity of the endothelial cells, and that 

 they then attract water from the tissue liquid, thus augmenting 

 the flow of lymph. These substances cause but little change in 

 arterial blood-pressure ; hence Heidenhain thought that the greater 

 flow of lymph can not be explained by an increased filtration. 

 Starling J has shown, however, that, although these bodies may not 



* "Journal of Physiology," 17, 30, 1894. 



t "Centralblatt f. Physiologic," 9, No. 2, 1895. 



j Loc. cit. 



