FOOD AND DIGESTION. 367 



First as to the function of the vagi in connection with the gastric 

 movements. Irritation of these nerves produces contraction of the stom- 

 ach, including the sphincter pylori. The vagi, then, are the motor 

 nerves to the stomach. 



Secondly as to the other nerve-fibres, which reach the stomach and 

 intestines through the solar plexus. These fibres pass from the spinal 

 cord in the anterior roots of the nerves from the sixth to the twelfth 

 dorsal, passing in the splanchnic nerves to the solar plexus, and thence 

 to the stomach. Stimulation of the splanchnics causes stoppage of the 

 muscular movements as well as relaxation of the sphincter pylori. 



It seems probable that automatic peristaltic contraction is inherent 

 in the muscular coat of the stomach, and that the central nervous system 

 is only employed to regulate it by impulses passing down by the vagi or 

 splanchnic nerves. 



Next as to the influence of the nerves on the secretion of the gastric 

 juice. It has been known for a long time that the secretion of gastric 

 juice could be reflexly stimulated. For example, Bidder and Schmidt 

 observed in a dog with a gastric fistula that the mere sight of food was 

 sufficient to cause a flow of gastric juice. Quite recently, Pawlow has 

 proved that secretory fibres are carried to the gastric glands in the vagus 

 trunk. His experiment consisted in establishing a gastric fistula, and 

 some days later in dividing the oesophagus in the neck in such a manner 

 that any food swallowed would be diverted to the exterior through the 

 cut end. " Fictitious meals " could then be given to the animal, and the 

 effect upon the stomach noted. As long as the vagi were intact, certain 

 foods (meats) caused a flow of gastric juice, though none of the food 

 reached the stomach. When the vagi had been cut, no secretion oc- 

 curred. Moreover, he found that direct stimulation of the vagus pro- 

 duced a flow of gastric juice. 



The subject has been still further elucidated by some experiments of 

 Heidenhain, relative to the normal mechanism of secretion. He cut 

 out a portion of the fundic end of the stomach, converting it into a 

 blind pouch opening to the exterior, while the continuity of the stomach 

 itself was established by sutures. Food given to the animal caused a 

 secretion in the cul-de-sac as well as in the stomach. From the experi- 

 ments he concludes that normally there occur a primary secretion due to 

 the mechanical stimulation of the mucous membrane and confined to 

 isolated spots, and a secondary secretion due to the absorption of the 

 products of digestion, which comes from the whole mucous membrane. 



Khigine has carried these experiments still further and obtained very 

 complete results. He has investigated the effects of various chemical 

 substances upon the flow of secretion,, and has found that peptone is the 



