FROM THE SMALL INTESTINE 637 



appeared in the fluid at the same time, this is probably true. 

 On the other hand, when the epithelium was damaged by using 

 strong dextrose solutions (15 per cent.), or solutions heated to 

 90 C., or by additions of NaF or liquor arsenicalis, this power 

 of the epithelium to keep back the blood NaCl was lost, and 

 the fluid in the gut might contain more than '6 per cent. NaCl 

 within twenty-five minutes. From this he concluded that the 

 normal living epithelium possesses an almost completely one-sided 

 permeability for NaCl of such a nature that the epithelium 

 is readily permeable from the gut towards the blood, but 

 impermeable in the opposite direction. He repeated Hamburger's 

 experiments on dead animals, using dextrose solutions, and found 

 the same slight absorption that Hamburger did ; he also found 

 that the NaCl in the solution at the end of the experiment was 

 under '2 per cent., in fact was not above that found in experi- 

 ments with living gut. He explained this result as being due, 

 not to the epithelium retaining after death its one-sided 

 permeability, but to there being no circulation, and consequently 

 no renewal of NaCl to diffuse into the gut. In order to prove 

 this point he repeated the experiments with an artificial circu- 

 lation of *9 per cent. NaCl carried on through the mesenteric 

 vessels. He then obtained a very different result ; the percentage 

 of NaCl in the fluid, remaining in the gut was about *7 per cent, 

 no absorption took place, and the osmotic pressure of the 

 solution introduced into the gut always rose, and did not tend 

 to approximate to that of the serum, as Hamburger found. 

 Cohnheim, in response to Hober's criticisms, has confessed that 

 these experiments on dead animals with an artificial circulation 

 are unsatisfactory, because the circulation was carried on too 

 long and at too high a pressure ; consequently the epithelium 

 may have been much altered, water-logged, and unable to absorb. 

 Hober has repeated Hamburger's experiments on dead animals, 

 using dextrose solutions. He was able to verify Hamburger's 

 results, but not those of Cohnheim, and he came to the con- 

 clusion that absorption in a dead intestine differs from that in 

 a living one quantitatively but not qualitatively. Nevertheless, 

 Cohnheim' s experiments prove that the normal epithelium 

 possesses a one-sided permeability, and in this he is confirmed 

 by Reid. We may therefore say that when the epithelium loses 

 this property in the course of an experiment, it is no longer in 



