306 PROD UCTION AND ABSORPTION OF L YMPH. 



From a consideration of these facts we must conclude that lymph 

 and saline solutions, isotonic with the blood, may be taken up by the 

 blood circulating through the capillaries, and that this process may 

 occur comparatively rapidly. 



Effect of intracapillary pressure. We have already seen how 

 any excess of intracapillary pressure, such as accompanies plethora, 

 causes an increased transudation from the capillaries, so that the 

 volume of circulating fluid is diminished. Now we see that, on any 

 diminution of capillary pressure taking place, as after bleeding, the 

 fluid in the tissue spaces goes back into the vessels to make up for 

 the volume of circulating fluid lost. This wonderful balance between 

 capillary pressure and lymph production or absorption is, I think, 

 well illustrated by Lazarus Barlow's observations. This author has 

 shown that the slight plethora produced by wrapping up a limb in 

 Esmarch's bandage causes an appreciable increase in the transudation in 

 other parts of the body, so that the specific gravity of the tissues of the 

 upper limb for instance falls, while the specific gravity of the blood 

 rises. The reverse is the case when circulation is restored to a limb 

 which has been kept ansemic for an hour or two. Here considerable 

 hypersemia of the affected limb is produced, and corresponding anaemia of 

 other parts of the body. We find, then, that absorption as well as trans- 

 udation through the capillary wall is determined by the intracapillary 

 pressure. When the pressure rises transudation is increased, when the 

 pressure falls absorption is increased. We have seen that the depend- 

 ence of transudation on capillary pressure is susceptible of a fairly simple 

 mechanical explanation. We have now to discuss the mechanism of the 

 absorption process. 



Mechanism of absorption. Filtration. Is absorption effected by 

 the active intervention of the endothelial cells, or are there physical 

 factors at work which will serve to explain it ? An explanation of 

 absorption, which will strike anyone who investigates this problem, is 

 that it may take place in the same manner as lymph is produced, 

 i.e. by a process analogous to filtration. A series of mechanical 

 experiments by Klemensiewicz l would seem at first sight to show 

 that such a backward filtration is impossible. Klemensiewicz points 

 out that, if fluid be passing at a given pressure through a permeable 

 tube contained within a rigid tube, transudation will occur until the 

 pressure of the transuded fluid is equal to that of the fluid flowing 

 through. At a certain point in the experiment the pressure of the 

 transuded fluid will exceed the pressure at the outflow end of the 

 tube. The tube will collapse and the flow through it will be stopped. 

 He imagines that the same sequence of events occurs in the living 

 body in the presence of a considerable transudation. Arteries, capil- 

 laries, and veins are bathed in the transuded fluid. The fluid which 

 leaves the capillaries will, if a free outflow for it be absent, after 

 a time attain a pressure near that ruling in the capillaries and higher 

 than the venous pressure. The veins will therefore collapse, venous 

 obstruction will be produced, and the capillary pressure and trans- 

 udation will be higher than ever, so that we have a vicious circle 

 of events tending continually to increase the oedema of that part. 

 Now Klemensiewicz' objections are true only under one condition i.e. 

 that the venous tubes should run freely through the lymphatic spaces of 



1 Sitzungsb. d. k. ATcad. d. Wissenscli., Wien, 1881. Bd. Ixxxiv.; 1886, Bd. xciv. 



