PHYSIOLOGY OF CYTOST ACTION 77 



somatic and splanchnic areas. Because of this, dila- 

 tion of the peripheral vessels is normally accom- 

 panied by contraction of the vessels of the splanchnic 

 area. The latter, in fact, may be regarded as a reser- 

 voir or regulatory apparatus for the entire circula- 

 tion, blood passing from this area to the peripheral 

 vessels when these are adequately stimulated. Con- 

 versely, stimulation of the abdominal vessels, by func- 

 tional activity or any other means, results in an in- 

 creased flow of blood through the splanchnic vessels. 

 We know that upon passing from a cool into a warm 

 atmosphere, the peripheral vessels dilate; upon re- 

 turning to the warm atmosphere, the peripheral ves- 

 sels rapidly contract, forcing the blood back to the 

 splanchnic area. In consequence, the vessels of the 

 latter dilate to accommodate the increased influx of 

 blood. Such facts as these illustrate the extreme deli- 

 cacy of circulatory regulation. 



In a previous chapter, there has been presented ex- 

 perimental evidence showing that direct stimulation 

 of the gastrointestinal mucosa promptly causes a lo- 

 cal hyperemia. If the stimulation be excessive, as by 

 the prolonged action of mustard in the stomach, or the 

 air blast, then this hyperemia becomes pathological 

 and eventually results in a marked venous congestion. 



The pronounced sensitiveness of the splanchnic ves- 

 sels to stimuli is a necessary function, the mild hyper- 

 emia following such stimulation being necessary for 

 the secretory and absorptive processes of the stomach 

 and intestines. Such mild dilation of the capillaries 

 of this area does not result in any obvious outward 

 symptoms. When, however, such dilation becomes 

 excessive, the diminished blood flow in the peripheral 



