MOVEMENTS OF THE ALIMENTARY CANAL. 643 



carbohydrate food begins to pass out from the stomach soon after 

 ingestion, and requires only about one half as much time as the pro- 

 teids for complete gastric digestion. Fats remain long in the stomach 

 when taken alone, and when combined with the other foodstuffs 

 markedly delay their exit through the pylorus. This distinct 

 difference in the main foodstuffs can hardly be referred to mere 

 mechanical consistency, since the fats are liquefied by the heat of the 

 body. There is an indication, therefore, that the relaxation of the 

 sphincter may be controlled in some way by chemical stimuli 

 originating in the digested food. 



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 it seems probable that its orderly 

 movements may be merely regulated through these extrinsic fibers, 

 and that it is essentially an automatic organ. Thus, it has been 

 shown that the excised stomach (Hofmeister and Schiitz) 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 the older observers* that gastric digestion may proceed normally 

 both as regards secretion and movements after section of the 

 extrinsic nerves. The point has not yet perhaps been demonstrated 

 conclusively, but provisionally we may regard the stomach, con- 

 sidered as a motor mechanism, as an automatic organ like the heart. 

 Its stimuli to movement arise within itself, but these movements 

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

 adapt them to varying conditions. Whether the automaticity is a 

 property of the plain muscle tissue itself, or depends upon the rich 

 supply of intrinsic nerve ganglia (plexuses of Meissner and Auer- 

 bach), is a question that can not be answered at present. 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 



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

 p. 118. 



