308 ENDOCRINE GLANDS 



of one of the systems. If we study a patient, keeping 

 these facts in mind, we are struck by the discovery of 

 certain findings which seem to disprove the preced- 

 ing conclusions. 



Let us take a practical example. Should we depress 

 the parasympathetic system, what do \ve observe? In 

 all parts of the organism where the parasympathetic 

 system is represented there will be hypotonia, that is, a 

 retardation of the functions in progress, but on the other 

 hand, in those parts of the body which receive both 

 sympathetic and parasympathetic enervation, phenomena 

 will appear which will be equivalent to stimulation of the 



HyPERTONIA 



HyPOTONJA 



Fia. 30. Diagrammatic demonstration of the paradox of tonus. 



sympathetic in those parts. This is what has been 

 termed the paradox of tonus, due to the fact that as the 

 parasympathetic tonus decreases, the sympathetic tonus, 

 which was balanced by it, becomes predominant and 

 appears as a hypertonia of the sympathetic. 



There is, therefore, a balance of tonus of the two systems 

 whenever they are present together. If for one cause or 

 another, by action on one or the other, the equilibrium is 

 disturbed, as one is depressed, the other automatically 

 becomes more prominent. 



The following mechanical example illustrates this 

 phenomenon and its significance. Suppose we take a 

 weight A in equilibrium between two equal forces. If 

 we wish to displace the weight towards C we can accom- 

 plish this in two different ways. By increasing the 





