FUNCTIONS OF THE STOMACH. 303 



coeliac-plexus extensions, hastens the speed of the Uood-flow 

 through the gastric tissues; (2) the oxidizing plasma, by enhanc- 

 ing metabolism, raises the temperature of the stomach at least the 

 1.5 C. required to render the formation of hydrochloric acid pos- 

 sible. 



The acid is thus formed when needed: a feature quite 

 in accord with experimental data. The parietal cells of the 

 glands, which are the seats of its formation, are only active 

 during digestion, and then increase in size; they continue in 

 this condition as long as the stomach contains food, and then 

 return to their normal size. The following lines of Howell's 

 also tend to indicate that our conception of the process may 

 be the right one: "The chemistry of the production of free 

 HC1 also remains undetermined. No free acid occurs in the 

 blood or the lymph, and it follows, therefore, that it is manu- 

 factured in the secreting cells. It is quite evident, too, that 

 the source of the acid is the neutral chlorides of the blood; 

 these are in some way decomposed, the chlorine uniting with 

 hydrogen to form HC1, which is turned out upon the free 

 surface of the stomach, while the base remains behind and 

 probably passes back into the blood." 



What is the role of the pneumogastric in this connection? 

 That it must be possessed of some regulative action upon the 

 circulation is shown by the fact that if, during digestion, i.e., 

 while the mucous membrane is congested and covered with 

 gastric juice, the pneumogastric is cut on both sides, pallor 

 of the surfaces at once ensues and the secretion is arrested. 

 If the central end i.e., that toward the brain be stimulated, 

 the membrane resumes its former color and the secretion is 

 re-established, while stimulation of the stomach end of the 

 nerve produces no effect, according to some observers. Paw- 

 low, however, as previously stated, obtained a marked secretion 

 in this manner probably by using a stronger current than did 

 his predecessors. We have previously suggested that the latter 

 result might have been due to the fact that the nerve acted 

 as a mere conductor; though an afferent nerve, the vagus must 

 thus have transmitted an electrical efferent impulse, while the 

 physiological impulse could not have been transmitted by it. 

 But this objection is removed when we link Pawlow's experi- 



