NERVOUS POWER. 357 



Experiments have shown that the due perform- 

 ance of the vital functions of digestion, of circu- 

 lation, and of secretion, requires the presence of 

 an agency, derived from different parts of the 

 brain and spinal marrow, and regulating the 

 order and combinations of the actions of the 

 organs which are to perform those functions. 

 The same influence, for example, which in- 

 creases the power of secretion in any particular 

 gland, is found to increase, at the same time, 

 the action of those blood-vessels which supply 

 that gland with the materials for secretion ; and 

 conversely, the increased action of the blood- 

 vessels is accompanied by an increased activity 

 of the secreting organ. Experience also shows 

 that when the influence of the brain and spinal 

 marrow is intercepted, although the afflux of 

 blood may, for a time, continue, yet the secretion 

 ceases, and all the functions dependent upon 

 secretion, such as digestion, cease likewise. 

 Thus the nervous power combines together dif- 

 ferent operations, adjusts their respective de- 

 grees, and regulates their succession, so as to 

 ensure that perfect harmony which is essential 

 to the attainment of the objects of the vital func- 

 tions ; and thus, not only the muscular power 

 which resides in the vital organs, but also the 

 organic affinities which produce secretion, and 

 all those unknown causes which effect the nutri- 



