474 GENERAL ANATOMY. 



section of the nerves of the lungs brings on speedily asphyxia 

 and death. 



The circulation, especially the action of the heart and capil- 

 lary arteries, is equally under the same influence. 



Secretion is also evidently under the influence of the nerves. 

 Direct experiments show that the section of the nerves of an 

 organ, suspends its secretion. Inhalation or absorption is 

 equally modified by the nervous action. Nutrition or organic 

 formation, without being an immediate result of the nervous 

 power, notwithstanding obeys its influence. Animal heat is 

 still more evidently dependent. The physiological experi- 

 ments of Messrs. Brodie and Chossat have placed this influ- 

 ence beyond all doubt: the chemical and physiological experi- 

 ments of Messrs. Dulong and Despretz have demonstrated 

 that this heat can not depend entirely on respiration. 



We see even in generation, that, the sensations and volun- 

 tary motions which accompany it, the motions of irritation, 

 the phenomena of secretion of the sperm and formation of the 

 ovules, those of the nutrition and growth of the fecundated 

 ovum, are all, but more or less directly, dependent on nervous 

 action. 



757. Sympathy or the co-existence of two phenomena of 

 formation, of irritation, of sensation or of volition, in the dif- 

 ferent parts, and by the action of a single agent, the most ex- 

 traordinary fact of organization, is yet an effect of nervous 

 action. 



758. What relation is there between the different parts of 

 the nervous system with respect to its functions? Is there a 

 single centre, either the spinal marrow, or the encephalon? 

 or are these two centres, viz. one cerebral and one ganglion- 

 ary ? or finally, are there as many distinct centres as there are 

 principal organs or great functions? These opinions, all found- 

 ed upon observation, are all true within certain limits. 



In the adult man, the nervous system forms a single system, 

 all the parts of which concur in the action of the whole, in 

 innervation, but besides each one in its proper function. 

 Thus the brain and the cerebellum, besides their particular 

 functions, augment the energy of the spinal marrow; this last 



