282 DIGESTION. 



never be decisive with such uncertain grounds of support, to show 

 that the gastric juice cannot be the cause of this acid reaction ; on 

 this point we would rather trust to the evidence afforded by well- 

 known experiments, which show that even after a flesh diet, which 

 gives an additional quantity of free acid to the gastric juice, the 

 acid reaction often entirely disappears in the jejunum. Putting aside 

 altogether my own observations and experiments, I would here 

 refer exclusively to the very admirable investigations of Bidder and 

 Schmidt* on this subject. After the common biliary and the pan- 

 creatic duct had been tied in a young dog, an intestinal fistula was 

 formed, which on the subsequent dissection of the animal was 

 found to communicate with the end of the upper third of the small 

 intestine. A week after the operation, when the wound might be 

 regarded as healed, and all general irritation seemed to have sub- 

 sided, the following experiments were instituted on the animal : 

 After feeding the dog with flesh, a greyish white mass, with a 

 strongly alkaline reaction, issued from the fistula ; in this case, 

 therefore, the free acid of the gastric juice and that of the flesh 

 itself was not only neutralised, but so much intestinal juice was 

 secreted that the alkalinity preponderated. In this case the alka- 

 linity cannot be referred to a formation of ammonia consequent on 

 putrefaction, which might perhaps have ensued from the suspension 

 of the flow of the bile ; for when the bile and pancreatic juice are 

 allowed free access to the intestine, we likewise find the chyme in 

 the jejunum and ileum equally alkaline. This much, however, 

 may be inferred from the above experiment, that the free acid 

 which we observe in the whole of the small intestine during a vege- 

 table non-acid diet, or after the use of sugar, does not depend upon 

 the gastric juice, but must have its source in the food itself. 



If the fact be confirmed that a portion of the starch and sugar 

 in the intestinal canal be converted into acid, we have then to 

 ascertain what substance, or what constituent of the intestinal 

 contents it is which induces this change. We have seen that 

 when the saliva, gastric juice, pancreatic fluid, and bile are totally 

 excluded, the intestinal juice itself is able to effect the metamor- 

 phosis of starch into sugar, and of the latter into lactic acid. 

 Moreover, starch was observed by C. Schmidt to be completely 

 changed by the intestinal juice into sugar in 30 minutes, and into 

 lactic acid in 5 or 6 hours. While we do not mean to deny that 

 gastric juice (Bouchardat and Sandras), bile (van den Broek) or 

 other fluids that make their way into the stomach, or, indeed, that 

 * Verdauungssaftc uud Stoffweebsel. Mitau, 1852, S. 271 u. 281. 



