MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 381 



semi-liquid mixture known as chyme, and in this condition the rhythmic 

 contractions of the muscles of the antrum eject it into the duodenum. The 

 rhythmic spirting of the contents of the stomach into the duodenum lias 

 been noticed by a number of observers by means of duodenal fistulas in dogs, 

 established just beyond the pylorus. It has been shown also that when the 

 food taken is entirely liquid — water, for example — the stomach is emptied in a 

 surprisingly short time, within twenty to thirty minutes ; if, however, the 

 water is taken with solid food then naturally the time it will remain in the 

 stomach may be much lengthened. 



A very interesting part of the mechanism of the stomach the action of 

 which is not thoroughly understood is the sphincter of the pylorus. During 

 the act of digestion this sphincter remains in a condition of tone ; whether 

 its tonic contraction is sufficient only to narrow the pylorus, or whether it 

 is sufficient to completely shut off the pylorus so that a partial relaxation 

 must occur with each contraction of the musculature of the antrum, is not 

 sufficiently well known. It has been shown, however, that this part of the 

 circular layer of muscle is distinctly under the control of the extrinsic 

 nerves, its tonicity being increased by impulses received through the vagi and 

 diminished or inhibited by impulses through the splanchnics. It will be seen 

 from the above brief description that the muscles of the antrum pylori do 

 most of the work of the stomach, while in the much larger fundus the food 

 is retained as in a reservoir to be digested and mechanically prepared for 

 expulsion into the intestine, the two parts of the stomach fulfilling therefore 

 somewhat different functions. Moritz l has called especial attention to this 

 fact, and points out the great advantage which accrues to the digestive pro- 

 cesses in the intestine in having the stomach to retain the bulk of the food 

 swallowed during a meal, while from time to time small portions only are 

 sent into the intestine for more complete digestion and absorption. In this 

 way the intestine is protected from becoming congested, and its digestive and 

 absorptive processes are more perfectly executed. 



Extrinsic Nerves to the Muscles of the Stomach. — The musculature 

 of the stomach receives extrinsic nerve-fibres from two sources: from the two 

 vagi and from the solar plexus. The fibres from the latter source arise ulti- 

 mately in the spinal cord, pass to some of the thoracic ganglia of the sympa- 

 thetic system, and thence by way of the splanchnics to the semilunar <>r solar 

 plexus and then to the stomach. These fibres probably reach the stomach as 

 non-medullated or sympathetic fibres. The vagi where they are distributed 

 to the stomach seem to consisl almosf entirely of non-medullated fibres also, 

 and probably the fibres distributed to the muscular coat arc of this variety. 

 The results of numerous experiments seem to show quite conclusively thai in 

 general the fibres received along the vagus path arc motor, artificial stimula- 

 tion of them causing mure or less well marked contractions of part or all of 

 the musculature of the stomach. It has been shown that the sphincter pylori 

 as well as the rest of the musculature is supplied by motor fibres from these 



1 Zeitschrift filr Biologie, 1895, Bd. xxxii. 



