636 THE MECHANISM OF ABSORPTION 



the mesenteric vein decreases, which suggests that a reduction 

 of circulation is the cause of the decreased rate of absorption ; 

 also below 8 mm. Hg absorption decreases, possibly because the 

 gut is less unfolded and the absorbing surface diminished. 



In order to prove that absorption was a purely physical 

 process, Hamburger carried out experiments on animals which 

 had been dead for varying periods up to twenty-five hours. The 

 rate of absorption could not be expected in the absence of a 

 circulation to be as great as during life, and if the difference 

 were in degree only, such experiments might be held to show 

 that physical processes play a correspondingly important part. 

 If, however, the absorption after death were found to differ in 

 kind also, then the experiments would prove nothing, but might 

 be held to indicate that vital activity of cells was essential to 

 normal absorption. Hamburger obtained results which appeared 

 to show that post-mortem absorption differed only in degree 

 from absorption during life. He found that 1'5 per cent. Nad 

 solution was absorbed at a rate of about '15 cc. per cm. of 

 gut per hour, which is less than a tenth of the rate of absorption 

 during life ; further, whilst in the living animal the osmotic 

 pressure of the solution in the gut becomes nearly isotonic with 

 the blood serum in twenty-five minutes, after death the osmotic 

 pressure of the solution had fallen only to that of a ] * 3 per cent. 

 NaCl solution in two hours. With blood serum in the gut the 

 actual rate of absorption was even less, and corresponded to 

 about a fifth of the absorption in a living animal. Hamburger 

 concluded that absorption in a dead animal differed in degree 

 only from that in a living animal, and took place presumably 

 by imbibition and filtration in the case of serum, and by diffusion 

 and osmosis as well in the case of anisotonic salt solutions. 

 Cohnheim, from his experiments, came to a very different con- 

 clusion, and believes that there is a real difference in kind 

 between absorption by living and by dead or damaged epithelium. 

 He studied the absorption of dextrose solutions, and at the end 

 of the experiment estimated the dextrose and NaCl in the 

 unabsorbed fluid. He found that with a normal intestine not 

 more than about '2 per cent. NaCl was to be found in this fluid 

 at the end of an experiment lasting two hours. He considered 

 that this NaCl was due, not to diffusion from the blood, but to 

 a secretion of succus entericus having taken place, and as Na 2 C0 3 



