3 o 4 PROD UCTION AND ABSORPTION OF L YMPH. 



difference in composition exists between intra- and extra vascular fluids, 

 so long will diffusion currents be set up tending to equalise this 

 difference. 



Absorption of isotonic fluids. These experiments, therefore, have 

 no direct bearing on the absorption of lymph, i.e. the normal tissue 

 juices. In this case the fluid to be absorbed resembles in almost all 

 particulars the blood plasma, and possesses the same osmotic pressure 

 as the latter, so that it would seem that there are no forces of diffusion 

 or osmosis tending to absorption. Mliller 1 concludes from similar 

 considerations that " the removal of collections of fluid must be effected 

 in many cases by means of the lymphatics, independently of imbibi- 

 tion into the capillaries." The mechanism of this lymphatic absorption 

 has been already studied. We have aow to inquire whether at any 

 time fluids, such as those normally present in the tissues and isotonic 

 with the blood, can be taken up by the blood vessels. 



We may arrange the experiments which have been made to decide 

 this point under three headings 



1. In the first set, observations were made on the absorption of 

 isotonic salt solutions and blood serum from the pleural and peritoneal 

 cavities. (Mow, 2 working under Heidenhain's direction, found that 

 such fluids were absorbed rapidly from the peritoneal cavities of living 

 animals, while the lymph flow from a cannula placed in the thoracic 

 duct showed no (or only slight) increase, in no way comparable to 

 the amount of fluid absorbed. He concluded, therefore, that the 

 absorption was effected by the blood vessels and was dependent on 

 the vital activity of the cells lining the serous cavities or of the 

 endothelial cells of the capillaries. Hamburger and Leathes con- 

 firmed these results, but showed that they could not depend on any 

 vital activity of the endothelial cells, since absorption took place with 

 equal rapidity even when poisonous solutions of sodium fluoride were 

 employed. 



The great objection to these experiments is that they do not prove 

 conclusively absorption by the blood vessels. It is still possible that the 

 fluids may have been taken up by the subserous lymphatic network -and 

 had not reached the thoracic duct during the experiment. This is an 

 objection raised by Cohnstein, 3 who concludes from very similar experi- 

 ments that these fluids are carried away solely by the lymphatics. It 

 might be thought that this question could be easily decided by observing 

 whether fluids were still absorbed from the serous cavities after ligature 

 of both lymphatic ducts. I have made a number of experiments of this 

 description, but have failed to get decisive results. It is true that, after 

 ligature of both thoracic ducts as well as of the right innominate vein, 

 isotonic salt solutions were taken up fairly quickly from the serous 

 cavities. In none of these cases, however, could I be certain that the 

 lymph was absolutely shut off from the blood. As a rule I injected 

 on three succeeding days several hundred c.c. saline solution into the 

 peritoneal cavity, the last injection containing carmine granules in 

 suspension. On killing the dog two days after the last injection, the 

 peritoneal cavity was generally found to be empty, and carmine granules 

 could be traced along the glands of the anterior mediastinum, showing 

 that, in spite of the ligature of both lymphatic ducts, there had been a 



1 Loc. cit. 2 Arck.f. d. ges. PhysioL, Bonn, 1894, Bd. lix. S. 170. 



3 Centralbl.f. PhysioL, Leipzig u. Wien, 1895, Bd. ix. 



