130 The Endocrine Organs 



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something which under ordinary circumstances acts as an inhibitory agent, 

 and we may suppose this to be present in the blood, and that it has been 

 furnished by the pancreas. 



The hypothesis that there exists a chalonic or inhibitory agent in the 

 internal secretion of the pancreas which affects carbohydrate metabolism 

 is probably the correct one. Whether this is of the nature of an autacoid or 

 of an enzyme cannot be definitely stated, although the supposition that it 

 is an autacoid is most in accordance with what is known regarding the 

 effective agents of other internal secretions. 



Relation of Internal Secretion of Pancreas with Other 

 Endocrine Organs 



Hyperglycemia is produced not only by extirpation of the pancreas, but 

 in various other ways, such as by Bernard's sugar-puncture of the medulla 

 oblongata, by stimulation of the splanchnics, and by the introduction of an 

 excess of adrenalin into the blood. 



We have seen that brushing the pancreas with adrenalin provokes 

 marked hyperglycemia and glycosuria, and that this is not merely due to 

 absorption of the autacoid into the general circulation is shown by the fact 

 that the excess of sugar is far greater than when other organs are so treated. 

 It is not, however, only through the pancreas that adrenalin glycosuria is 

 produced, for it has been shown by various observers that there is an in- 

 crease of sugar in depancreatised animals (also in cases of pancreatic diabetes 

 in man) as the result of adrenalin injection. Moreover, the effect of 

 adrenalin is produced immediately both in normal and in depancreatised 

 animals, whereas it takes some hours for the effect of depancreatisation 

 upon carbohydrate metabolism to show itself. On the other hand, Zuelzer 

 and others have found that adrenalin glycosuria is prevented by pancreas 

 extracts and even by pancreatic juice ; this effect is, however, according 

 to De Meyer, not due to an antagonising autacoid, but to the effect of the 

 extracts upon the permeability of the kidney for sugar. The result of 

 administering pilocarpine, which produces marked secretion from the 

 pancreas by exciting the secreting endings of the vagi, is also to prevent 

 adrenalin glycosuria ; possibly it acts by stimulating nerve-endings to the 

 islet cells as well. 



Loewy finds that after removal of the pancreas, adrenalin causes dilata- 

 tion of the pupil when dropped into the eye ; this does not occur in 

 the normal animal. The same observation has been made in cases of 

 diabetes in man — presumably these cases are of pancreatic origin. 



With regard to the relations between the pancreas and the thyroid and 

 parathyroids, it is found that removal of the thyroid tends to prevent, and 

 removal of the parathyroids to facilitate, both pancreatic and bulbar 

 glycaemia and glycosuria. The thyroid autacoid may therefore be regarded 

 as in this matter antagonistic to that of the pancreas, whilst the parathyroid 



