272 



FoL' various reasons the intestines of smaller animals, mouse, cavia, 

 rabbit, were chiefly experimented upon. The method followed here 

 keeps the intestines longer alive in proportion as tliej are thinner. 

 In reality this method is a very primitive one. In the intestinal wall 

 there is no longer any circulation and the metabolism is therefore 

 restricted to the diffusion through the whole thickness of the wall. 

 Hitherto I have not succeeded in keeping the gut alive in tyrode- 

 solution, a medium particularly fitted for intestine-experiments, for 

 a longer period than 5 days. Pieces of intestine which no longer 

 moved in the solution in which they had been placed immediately 

 after the extirpation, began to move again when the solution was 

 refreshed. This can easily be explained. 



' The experiuients carried out by collaborators of Magnus, Weinland 

 and Neukirch have taught that when the intestine is placed in a liquid 

 medium, substances are formed which stimulate the intestine. That an 

 accumulation of these stimulating substances, besides the usual decom- 

 position products, and more especially besides the bacterial decom- 

 position products, unavoidable in intestine-experiments,sliould impair 

 the activity of the intestine in the long run can easily be understood. 



If the temperature of the pieces is kept particularly low (± 3°), 

 then the intestine keeps alive much longer than if the temperature 

 remains but little under the limit at which activity still manifests 

 itself. Pieces of cavia gut in tyrode-solution at 15° were already 

 dead on the 3«i or 4''» day. 



If the temperature of the tyrode-solution was =b 3°, the gut died 

 only on the ö''*' day. 



To keep the gut alive for a longer period a medium is required 

 resembling more than tyrode-solution the normal body-fluids. For 

 this purpose 1 look korse-.seniia 'j. the serum of the small animals 

 experimented upon not being obtainable in sufficient quantities. 



Since oxygen must bubble through the fluid in which the gut 

 has been placed, a great quantity of froth is formed if serum is 

 taken instead of tyrode-solution. This can l)e avoided, however, by 

 pouring a thin layer of olive-oil OJi the serum. It might be assumed 

 as probable that serum would prove a better medium than a salt- 

 solution on the strength of the many experiences obtained with the 

 surviving heart. (White, Howell, Gkken, Waldkn, with hearts of 

 warmblooded animals, Guthrie and Pike with hearts of mammals. ^) 



1) Horse-serum can' be obtained by the method, described by Hamburger and 

 often applied in his laboratory, 1 lake lliis opportunity of again thanking my 

 colleagues De Haan and Ouweleen for the readiness with which they always 

 provided me with horse serum. 



