MOVEMENTS OF THE ALIMENTARY CANAL, ETC. 



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 stomach re- 

 ceives extrinsic nerve-fibres from two sources ; from the two vagi and from 

 the solar plexus. The fibres from the latter source arise ultimately in the 

 spinal cord, pass to some of the thoracic ganglia of the sympathetic system, 

 and thence by way of the splanchnics to the semilunar or solar plexus and 

 then to the stomach. These fibres probably reach the stomach as non-medul- 

 lated or sympathetic fibres. The vagi where they are distributed to the 

 stomach seem to consist almost entirely of non-medullated fibres also, and 

 probably the fibres distributed to the muscular coat are of this variety. The 

 results of numerous experiments seem to show quite conclusively that in general 

 the fibres received along the vagus path are motor, artificial stimulation of 

 them causing more 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 

 nerves. The fibres coming through the splanchnics, on the contrary, are 

 mainly inhibitory. When stimulated they cause a dilatation of the contracted 

 stomach and a relaxation of the sphincter pylori. Some observers have 

 reported experiments which seem to show that this anatomical separation of 

 the motor and inhibitory fibres is not complete ; that some inhibitory fibres 

 may be found in the vagi and some motor fibres in the splanchnics. The 

 1 Zeiischrift fur Biologie, 1895, Bd. xxxii. 



