720 PHYSIOLOGY OF DIGESTION AND SECRETION. 



before the protein, the former, having the position of advantage 

 toward the pyloric end, will be ejected promptly into the intestine, 

 while the protein is retained for gastric digestion. If the order is 

 reversed and the protein is fed first, the passage of the carbohydrate 

 out of the stomach will be retarded. This author has also reported 

 numerous interesting experiments, of medical and surgical interest, 

 which indicate that the motor activity of both stomach and intes- 

 tines may be greatly depressed by certain conditions, especially 

 by mechanical handling or by conditions of general asthenia. 



Regarding the general mechanism of the stomach, it may be 

 pointed out that it forms an admirably adapted apparatus for 

 receiving at once, or within a short period, a large amount of food 

 which it reduces to a liquid or semiliquid condition, partly by 

 digestion, partly mechanically, and that it charges the intestine 

 at intervals with small amounts of this chyme in such a condition 

 as to admit of rapid digestion. It seems obvious that without the 

 stomach our mode of eating would have to be changed, as it would 

 not be possible to load the intestine rapidly with a large supply of 

 food such as is consumed at an ordinary meal. 



The Relation of the Nerves to the Movements of the 

 Stomach. — The stomach receives nerve fibers from two sources, — 

 the vagi and the splanchnics, — but its orderly movements are merely 

 regulated through these extrinsic fibers; it is essentially an auto- 

 matic organ. Thus, it has been shown that the excised stomach 

 (Hofmeister and Schutz), when kept warm, continues to execute 

 regular movements which, if not identical with those observed under 

 normal conditions, have at least an orderly sequence. So also it 

 would appear from the results of several observers * that gastric 

 digestion may proceed normally both as regards secretion and 

 movements after section of the extrinsic nerves. We may regard 

 the stomach, considered as a motor mechanism, as an automatic 

 organ like the heart. Its stimuli to movement arise within itself, 

 probably within its intrinsic nerve plexus, but these movements 

 are regulated by the action of the extrinsic nerve-fibers so as to 

 adapt them to varying conditions. The extrinsic nerves not only 

 supply the stomach with efferent fibers, motor and secretory, but 

 also carry afferent fibers from the stomach to the central nervous 

 system. Regarding the purely efferent action of the extrinsic 

 nerves, the results of numerous experiments seem to show quite 

 conclusively that in general the fibers 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 



* See Heidenhain in Hermann's "Handbuch der Physiologic," vol. v, 

 p. 118. Also Cannon, "American Journal of Physiology," 1906. 



