ABSORPTION OF LYMPH 283 



physiological regulation and the pathological variations in the 

 lymph flow ? They are purely physical or mechanical causes, 

 and the '" vitalist " school will claim that they are inadequate and 

 that " vital activities " of the cells play the deciding role. But 

 at present the evidence that is being accumulated seems to point 

 more and more strongly to the conclusion that these " vital activ- 

 ities " are but the result of simple well-known physical forces 

 acting under very complex conditions complex because of the 

 large number of very different chemical compounds occurring 

 together, and the varying influence of circulation, food supplies, 

 cell structure, etc. 



ABSORPTION OF LYMPH 



By no means all the fluid that escapes from the vessels, 

 nor all the products of cell metabolism are carried away in 

 the lymph a considerable and perhaps the greater part of them 

 is absorbed back into the capillaries directly. A classical proof 

 of this is the experiment of Magendie, who observed that if 

 poisons were injected into the leg of an animal, which had been 

 separated from the body entirely except for the blood-vessels, 

 that poisoning developed in the usual manner. In such experi- 

 ments the lymph-vessels are severed and probably largely 

 occluded, hence it does not solve the question as to whether 

 substances are absorbed by the blood-vessels under normal con- 

 ditions. Orlow found, however, that during absorption of fluid 

 from the peritoneal cavity there is no perceptible increase in the 

 lymph flow from the thoracic duct. Addition of sodium fluoride, 

 a protoplasmic poison, was found to interfere with this absorp- 

 tion, for which and other reasons Heidenhain and Orlow con- 

 sidered that the absorption depended upon the " vital activity " 

 of the cells. More nearly reproducing normal conditions were 

 the experiments of Starling and Tubby, who found that 

 methylene-blue or indigo-carmine injected into the pleura or 

 peritoneum appeared in the urine long before it colored the 

 lymph in the thoracic duct. 1 Adler and Meltzer found evidence, 

 however, that not all the absorption is accomplished by the 

 blood-vessels, for obstruction of the thoracic duct retards absorp- 

 tion. That the absorption is not dependent solely upon the 

 circulation and blood pressure is shown by the fact that absorp- 

 tion from the peritoneal cavity occurs in dead bodies (Ham- 

 burger, Adler and Meltzer). 



The nature of the mechanism by which fluids are taken into 



1 See Mendel, Amer. Jour. Physiol., 1899 (2), 342. 



