On the Relations between the „Islets of Langerhans" etc. 85 



is the arrival of tlie acid chyme in the duodenum, the withhokling of 

 food would involve a storeage of material in the gland cells. But, 

 assuming that under normal conditions alveoli are being constantly 

 converted into islets and islets back again into alveoli, and that the 

 first of these processes is an expression of a constant tendency of the 

 gland tissue to revert to an embryonic condition; then we may con- 

 ceive that in inanition the first process may regularly proceed, while, 

 owing to the absence of food to be digested the second may be in 

 abeyance. 



Moreover the discharge of secreted material is always going on, 

 involving a progressive increase in the amount of islet tissue, and the 

 absence of absorbed' food material may render it difficult or impossible 

 for the more highly differentiated zymogenous tissue to be reproduced. 



IV. Effects of Exhaustion of the Mammalian Pancreas. 



For this investigation we have used the method employed by Dale. 

 The dogs wei'e anaesthetized with morphia and the A C. E. mixture, 

 and secretin ^) solution at body temperature was injected into the saphe- 

 nous vein at intervals throughout a period of 7, 8, 9, 10 or more hours. 



On examining the gland microscopically, in addition to the ordi- 

 nary signs of exhaustion, we have found a decided increase in the 

 amount of islet tissue, but in our experiments this has never been so 

 pronounced as after inanition (see PI. IV, Fig. 4 and cf. with PI. IV, 

 Fig. 3 and PL IV, Fig. 5), 



There is no need to describe the changes in detail, since, although 

 they differ in degree, they seem identical in character with those in- 

 duced by the withholding of food. The results are perhaps, however, 

 of greater theoretical importance, since a change which can occur within 

 a few hours can scarcely be interpreted as a morphological one, but 

 must, on the other hand, be considered as representing a phase of 

 physiological activity. We shall refer to this subject later. 



Tlie secretin experiments then furnish further evidence of the inter- 

 changeability of islets and zymogenous tissue. 



1) Bayliss and Starling, Jonrn. of Physiol., Vol. 28, p. 825, 1902; Vol 29. 

 p. 174, 1903. 



