REGULATORS Gil 



and is based upon Biedl's experiments upon fish (p. 610), and 

 Vincent's experiments on mammals (p. 591). 



The Interaction of the Endocrinetes. 



The endocrinetes, with their internal secretions, exercise a 

 balanced influence on the metabolism. 



This is very clearly shown by the reciprocal action on the 

 mobilisation of sugar of the chromaffin tissue and thyreoid on 

 the one hand, and of the pancreas on the other, the two former 

 stimulating it, the latter checking it. 



There is also evidence that they act upon one another. 

 Thus, while thyreoidectomy has not been show^n to have any 

 influence upon the adrenalin content of the chromaffin tissue, 

 feeding with thyreoid does increase it. The true pituitary and 

 the thyreoid exercise an influence on the growth and on the 

 functional activity of the gonads, and they in turn are acted 

 upon by the gonads. 



In some cases these structures seem to supplement one 

 another. The thymus, testis, and anterior lobe of the pituitary 

 all seem to combine in maintaining growth in the young. 



Mode of Action of Internal Secretions. 



The study of the action of these internal secretions involves 

 the question of how far they act independently of or through 

 the nervous system. The evidence that adrenalin acts through 

 the nerve structures appears to be conclusive, and in all proba- 

 bility the products of the hypophysis, the thyreoid, and the 

 pancreas act in the same way. On the other hand, in domin- 

 ating the growth and development of the body in early life, it is 

 very possible that the thymus and gonads, possibly the thyreoid 

 and pituitary, act directly upon the tissues. If this be so, the 

 internal secretions may act (1) as primary chemical regulators 

 and (2) as neuro-cheniical regulators. 



The influence of the various factors dominating metabolism, 

 growth, and development, might be represented in fig. 232, 

 where the influence of hereditary inertia is shown as dominant 

 in embryonic life ; where the influence of the nervous system 



