INTERNAL SECRETIONS 



385 



rally, and especially on the muscles of the vascular system, 

 causing contraction of the arterioles, and an enormous rise 

 in the blood-pressure. It seems to act not directly on the 

 muscle substance, but rather through the sympathetic nerve 

 endings. Thus, McFie got no action on the heart of the chick 

 in which the nerves are not yet developed, while Brodie has 

 failed to get any effect on the vessels of the lungs in which 

 the sympathetic nerve terminations are said to be absent. 



FIG. 151. Section through Cortex and Medulla of the Suprarenal Body of 

 a mammal ; a, 6, c, d, Cortex ; /, Medulla. 



Apocodeine, which poisons the nerve endings, abolishes the 

 effect of suprarenal extracts on the blood vessels. 



On the heart it has an inhibitory action through the 

 vagi, and this may be removed by section of the nerves or 

 by the administration of atropine, which poisons their termi- 

 nations. 



As already indicated (p. 368), injections of extracts of the 

 suprarenal bodies profoundly modify the metabolism, lead- 

 ing to an increase of sugar in the blood and to its excretion 

 in the urine. This is best marked when the animal is well 

 fed and has a store of glycogen in its liver, but since it 

 occurs in fasting animals after the stored carbohydrates 



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