634 THE MECHANISM OF ABSORPTION 



1 mm. per sec. must indeed be small. Hamburger apparently 

 looks upon it as a force which determines, not so much the 

 absorption of fluid from the lumen of the gut, as the passage 

 of fluid from the connective space into the blood capillary rather 

 than into the lymphatic ; for the rate of flow in the blood capil- 

 lary is probably far greater than in the lymphatic. 



Filtration is, according to Hamburger's view, the most impor- 

 tant force in absorption. Leubuscher had previously maintained 

 that a slight increase of intra-intestinal pressure favoured absorp- 

 tion, and he explained the result not by filtration, but by an un- 

 folding of the mucous membrane increasing the absorbing surface. 

 Hamburger eliminated this factor by enclosing a coil of intestine 

 in a rigid tube which was so arranged that the coil, whilst filling 

 the tube, retained its normal blood supply. The coil was filled 

 with '9 per cent. NaCl solution and connected with a reservoir of 

 the same fluid. The maximal intra-intestinal pressure used corre- 

 sponded to about 10 mm. Hg, and he found that up to that 

 point the rate of absorption varied directly with the pressure. 

 In other experiments the intra-intestinal pressure was raised by 

 blowing air into a closed abdominal cavity ; the maximal pressure 

 used was about 8 mm. Hg, and the result on absorption was 

 the same as before. In yet another series of experiments he 

 investigated the effect on absorption of reducing the intra- 

 intestinal pressure to zero. For this purpose he sucked the gas 

 out of a coil, and, in order to prevent the coil from collapsing, 

 he introduced into it a cage made of aluminium wire. He found 

 that no absorption of '9 per cent. NaCl solution took place when 

 the pressure was zero or negative, but that if the intra-intestinal 

 pressure were raised to as little as '04 mm. Hg, absorption 

 began and increased with the pressure up to 17 mm. Hg., the 

 maximal pressure used. If these experiments were true and 

 contained no fallacy, they would militate greatly against Ham- 

 burger's own view. For, when the pressure was zero and no absorp- 

 tion took place, imbibition and aspiration by the capillary blood 

 flow could still occur ; and yet not a drop of fluid was absorbed. 

 Further, osmosis and diffusion could still take place, for it is 

 well known that if a *9 per cent. NaCl solution is separated from 

 serum by a membrane permeable to NaCl and water, such as he 

 supposes the gut to be, absorption readily takes place. The 

 fallacy of the experiments with reduced pressure would appear 



