THE ADRENALS 27 



When the vagus nerves are intact, the rise of 

 blood-pressure is less, because, in accordance with 

 Marey's law, slowing of the heart takes place. 

 The action of adrenalin is not confined to the blood- 

 vessels, but extends to every structure of the body, 

 which is normally supplied with nerve fibres from 

 the sympathetic system. It stimulates the nerve 

 endings of these fibres in the structures which 

 they supply, and the results of the injection are 

 identical with those of stimulation of the entire 

 sympathetic system. Thus it increases the force 

 and (if the vagi are divided) the rate of the heart, 

 and at the same time dilates the coronary vessels, 

 so that in spite of the rise in arterial pressure the 

 efficiency of the heart is maintained and its out- 

 put may even become larger." This effect on 

 the coronaries is very important, and helps to 

 explain its great therapeutic value in some con- 

 ditions of dyspnoea. Its action on the movements 

 of organs of digestion is rather inhibitory, and it 

 may cause dilatation of the pupils. 



The arteries that are most affected are those 

 of the splanchnic area and the cutaneous vessels 

 all over the body ; the pulmonary arteries and 

 the cerebral are very slightly influenced. 



Schafer says, " It is always the smaller vessels 

 which are most affected, and in consequence of 



