306 ENDOCRINE GLANDS 



logical methods of progression of the vegetative systems of 

 co-ordination, the vegetative association tracts. At the 

 beginning I have explained the morphology of these 

 systems and I will not repeat again. I will content myself 

 to indicate that in a general way the pathways of vegeta- 

 tive life do not differ essentially -from tracts found in the 

 nervous axis and in the brain. 



V. PHYSIOPHARMACOLOGICAL OPPOSITION OF THE 

 TWO GREAT VEGETATIVE SYSTEMS. 



We have just seen that by their physiological opposition 

 we can divide the vegetative system into two groups; 

 the sympathetic and parasympathetic. This opposition 

 becomes still more evident if we study these two systems 

 from a pharmacological point of view. 



I. ELECTIVE ACTION OF CERTAIN SUBSTANCES OX THE 

 VEGETATIVE SYSTEMS. 



When we study substances which we consider as prod- 

 ucts of internal secretions, 14 we are struck by the fact 

 that they have an elective action upon the systems of 

 vegetative life, for their introduction into the organism 

 stimulates, or depresses, the action of these systems. 

 This is a fact of prime importance. 



It is not necessary at present to go into details of the 

 pharmocodynamic action of the organo elective substances. 

 We will come back to this presently. At present we shall 

 study certain more general facts on the action of the 

 various substances on the vegetative nervous systems. 



II. PHARMACOLOGICAL ANTAGONISM OF THE NER- 

 VOUS SYSTEMS OF VEGETATIVE LIFE. 



The substances having an elective action on the nervous 

 systems of vegetative life can be divided into two groups: 



14 The extracts of organs are not necessarily identical to hormones. 



