FUNCTIONS OF THE STOMACH. 307 



bach and Meissner plexuses. The need of such an arrange- 

 ment at once suggests itself, however, when the influence of 

 stimulus applied to the membrane soon after ingestion of the 

 stimulating agency, as thought by Heidenhain, or some time 

 after, as thought by Pawlow, is recalled. 



The sensory filaments of the vagus could alone, from our 

 point of view, produce such results, since we attribute only 

 efferent impulses to the other nerves which all belong to the 

 great motor system. This is sustained by the classical experi- 

 ment previously referred to, in which stimulation of the cen- 

 tral end of the cut vagus caused the secretion to reappear a 

 fact which also demonstrates that the vagus is an autono- 

 mous system: i.e., endowed with afferent and efferent nerves. 

 Whether the branches distributed to the solar plexus and the 

 gastric extrinsic vessels are afferent or efferent nerves can now 

 easily be determined. As the functions of the stomach are 

 similar to those of the salivary glands, as previously shown, 

 the increase of secretion caused by stimulation of the stump 

 can only have been caused by conveying additional impulses 

 to the normal motor-constrictor impulses and to the rest -of 

 the motor functional mechanism: a feature which suggests 

 that the general motor mechanism (sympathetic) serves to main- 

 tain the tonic contraction of the gastric vascular supply and the 

 immanent potentiality of the stomach when it is in the passive 

 state, while the added impulses of the pneumogastric bring on 

 functional activity. In other words, the great motor system 

 officiates during the passive state, while the vagus system is 

 superadded during the active state. 



We can now understand why section of both vagi produces 

 no effect: the motor nerves continue to maintain the tone of 

 the vessels and everything goes on as usual. If these motor 

 nerves are also severed, however, we have general relaxation, 

 as previously explained, and engorgement secretion. Again, 

 we can better understand the effects of violent emotion upon 

 digestion when it becomes possible to ascribe to a single center 

 or area the effects of the morbid excitement. If the motor 

 system bore the brunt of such influences, these would in- 

 duce general vascular dilation by lowering functional activity, 

 since the said system sustains general vascular tone: again, 



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