6 John Rennie, 



of the gland by means of secretin. True exhaustion of the mammalian 

 gland was not found possible unless the animal was also bled. This 

 suggests that secretin stimulates both anabolic and katabolic activity 

 of the pancreatic cells, and that anabolism must be otherwise depressed 

 if the exhaustion effect is to be produced . . . The proportion of islet 

 tissue to secreting tissue is also increased by prolonged fasting. In 

 other words disappearance of the stored material of the secretory cell, 

 whether by discharge into the duct, to produce the secretion, or by 

 absorption into the blood and lymph, when the nutrition of the body 

 fails, is attended by increased formation of islets from secretory 

 alveoli . . . Occlusion of the duct causes disappearance of most of the 

 pancreatic tissue in the course of a few weeks. That which escapes 

 destruction assumes a form resembling the islets, but the already 

 existing islets exhibit no special immunity from the destructive effects 

 of the operation." It is Dale's opinion that this change is a "reversion 

 to an embryonic type". Vincent and Thompson have still more recently 

 practically repeated the work of Diamare, Rennie, and Dale. They 

 confirm the morphological results of the two former authors, including 

 the existence in bony fishes of the permanent "principal islet" described 

 by Kennie. On the physiological side they fully confirm the results 

 of Dale, and on this account, coupled with the fact that they find 

 apparently abundant evidence of transformations of tissue in progress 

 apart altogether from experiment in the normal pancreas, they adopt 

 the view that there is a functional interdependence of the two tissues. 

 Their more important conclusions are: "The islet columns are frequently 

 in complete anatomical continuity with the surrounding zymogenous 

 tubules, and all kinds of transition forms are common throughout 

 vertebrates ... In mammals (dogs and cats), birds (pigeons), and 

 amphibians (frogs) the effect of inanition is to markedly increase the 

 amount of the leptochrome islet tissue, at the expense of the zymo- 

 genous tissue. In this condition direct continuity and transition forms 

 are even more marked than in the normal animal. If after a period 

 of inanition, an animal be restored to its normal condition, the pancreas 

 likewise retui-ns to the normal, and the presumption is that alveoli 

 are reconstructed from islets. An increase in the amount of islet tissue 



