738 



PHYSIOLOGY 



food in the stomach. This combined character of the gastric juice produced 

 by a normal meal is shown in the following Table (Pawlow) : 



SECRETION or GASTBIC JUICE 



In the first column is given the result of a normal meal on the secretion 

 from the gastric diverticulum. In the second column are given the amount 

 and digestive power of the juice which is excited by the direct introduction of 

 150 grm. of meat into the large stomach of the animal, care being taken not 

 to excite in Any way the nervous reflex mechanism. In the third column 

 are given the amount and digestive power of the juice which is evoked by a 

 sham meal of 200 grm. of meat. In the fourth column is given the sum of 

 the last two experiments. It will be seen that the total effect of the sham 

 meal plus the direct introduction of meat into the stomach is almost identical 

 with the secretion obtained when the food is taken in a normal way and 

 allowed to pass through the oesophagus into the stomach. 



The second phase of the gastric secretion cannot be ascribed to the inter- 

 vention of the reflex vagal mechanism. Since it occurs after cutting off the 

 stomach from its connections with the central nervous system, it must have 

 its causation in the gastric walls themselves. That it cannot be due to 

 mechanical stimulation is shown by the fact, previously mentioned, that 

 it is impossible by local stimulation of the mucous membrane, by rubbing, 

 by introduction of sand, or any other method, to evoke a secretion. Moreover 

 it is not produced by all sorts of food. The introduction of white of egg, of 

 starch, or of bread into the stomach causes no secretion. On the other hand, 

 if bread be mixed with gastric juice and allowed to digest for some time, the 

 introduction of the semi-digested mixture into the stomach evokes a secre- 

 tion. We have already seen that meat produces a secretion; still more 

 potent than meat however is a decoction of meat, or bouillon, or Liebig's 

 extract of meat, or certain preparations of peptone. Pure albumoses and 

 peptones have no effect, so that* the exciting mechanism must be some 

 chemical substances present in meat, and produced in various other foods 

 under the action of the first gastric juice secreted in response to nervous 

 stimuli. Popielski has shown that this secretion occurs after complete 

 severance of the stomach from the central nervous system, as well as after 

 destruction of the sympathetic nervous plexuses of the abdomen. Since 



