LYMPH ABSORPTION 607 



but that which had passed through the cedematous leg in- 

 variably became less concentrated, showing that fluid had been 

 taken up. 



Starling has also pointed out that the old observation that 

 after venesection the blood becomes less concentrated, was to be 

 explained in exactly the same way, by the taking up of isotonic 

 fluid from the tissue spaces ; a conclusion which is confirmed by 

 Lazarus-Barlow's observation that after bleeding the sp. gr. of the 

 tissues rises, and by Hamburger's observation that the A of the 

 blood serum is unaltered. 



Lazarus-Barlow's observations further show the part played by 

 the tissue fluids in keeping the volume of the circulating blood 

 normal. He found that if the hind legs of a dog were tightly 

 bandaged from below upwards, the then overfilled vascular 

 system got rid of its surplus fluid into the tissue spaces within an 

 hour; for the sp. gr. of the tissues fell and that of the blood 

 plasma rose. Conversely when the bandages are taken off the now 

 underfilled vascular system takes up fluid from the tissue spaces, 

 for the sp. gr. of the plasma falls and that of the tissues rises 

 within an hour to normal. 



Absorption from the serous cavities might differ materially from 

 that taking place from the connective tissue spaces. For not 

 only are there stomata opening direct into the lymphatics, but 

 material would have to pass through the endothelium lining the 

 cavity before it could reach the capillary. 



Starling and Tubby showed that methylene-blue or indigo- 

 carmine introduced into the serous cavities appeared within five 

 minutes in the urine, and not in the thoracic duct for half-an- 

 hour or more. This result was denied by Adler and Meltzer on 

 mistaken grounds, and was confirmed by Mendel and by Starling 

 himself. Absorption by blood-vessels was therefore proved. 



The importance of experiments on absorption from serous 

 cavities has not been in deciding whether blood-vessels absorb at 

 all or can absorb an isotonic fluid, but in showing the interchanges 

 between the blood and fluid which take place during absorption, 

 and the relative importance of blood-vessels and lymphatics. 



The researches of Leathes and Starling, Hamburger, and Roth 

 and many others, have shown the nature of the interchanges 

 between the blood and fluid injected into the pleural or peritoneal 

 cavity. If the fluid is a hypotonic salt solution, the following 



