LYMPH ABSORPTION 611 



per cent. He associates these differences with different permea- 

 bilities of the capillary walls for proteid. Granted that this is so, 

 certain corollaries follow. (1) The more impermeable the capillary 

 the greater will the blood pressure have to be in order to drive 

 proteid through. Correspondingly we find that the capillary 

 pressure in a limb is about 20 mm. Hg, in the liver about 

 5 mm. Hg, and in the intestines something intermediate between 

 the two. But it is equally true that, if the permeability of the 

 capillary walls were the same in all three areas, the difference in 

 capillary pressure would explain the different concentrations of 

 colloid in the filtrate according to the laws of filtration. (2) The 

 more impermeable the capillary wall the more will a rise in 

 capillary pressure increase the force tending to absorption by 

 decreasing the concentrations of colloid in the filtrate. In this 

 way Starling explains the apparent fact that in a limb there 

 may be no flow along the lymphatics although transudation is 

 presumably taking place. On the other hand, in the areas 

 drained by the thoracic duct there is a constant flow of lymph, 

 which is rapidly accelerated by any increase in transudation. In 

 the same way he would explain the different effects on lymph flow 

 in a limb produced by ligature of the veins, and vaso-dilatation of 

 the arteries. In the former there is increased transudation and 

 decreased absorption, but in the latter increased transudation and 

 a nearly corresponding increase in absorption. 



These views of Starling on the part played by the osmotic 

 pressure of proteids in determining absorption have been criticised 

 by Moore and Parker. The premises necessary for his view are 

 a relative impermeability of the capillary to proteid, and con- 

 sequent differences in concentration of proteid on its two sides. 

 They point out that the former has never been shown by direct 

 experiment, and that the latter is incapable of proof ; for we 

 cannot obtain tissue fluid, but only its overflow into the lymphatics 

 after the tissues have removed some proteid from it. They 

 would explain the different percentage of proteid in lymph 

 as compared with blood, and in lymph from different parts of 

 the body, by the varying amounts of proteid abstracted from 

 the tissue fluid by the tissues. From this it would follow that 

 anything which increased the rate of flow of tissue fluid through 

 the tissues must also increase the percentage of proteid which the 

 lymph contains. This is often the case, but by no means always 



