INTERNAL SECRETIONS OR HORMONES 405 



in the blood pressure. That the action is upon the endings of 

 these nerves is shown by the fact that McFie found 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 termina- 

 tions are said to be absent. Further, apocodeine, which poisons 

 the nerve endings, abolishes the effect of suprarenal extracts. 



Cardiac inhibition is produced but this may be due to the 

 rise of blood pressure. It is abolished by the administration of 

 atropin. 



These extracts also cause a dilatation of the pupil in the 



FIG. 163. Section through Cortex and Medulla of the Suprarenal Body 

 of a Mammal ; a, b, c, d, cortex ; /, medulla. 



cat and it inhibits intestinal peristalsis. Their action on the 

 bladder varies according to the action of the sympathetic fibre, 

 which is different in different animals. In those in which these 

 fibres cause contraction, extract of the suprarenal acts in this 

 way ; in those in which relaxation is caused, the extract causes 

 relaxation. With blood vessels which are not supplied with 

 vaso-constrictor fibres, e.g. those of the lungs and heart, the extract 

 does not act, and hence a rush of blood to the lungs is caused. 



As already indicated (p. 389), injections of extracts of the 

 suprarenal bodies profoundly modify the metabolism, leading 

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



