62 Swale Vincent and F. D. Thompson, 



the end of this paper (p. 28). We shall endeavour as far as possible 

 to make reference to all important previous work upon the subject, 

 but we crave pardon for any unintentional omissions, since we are 

 many houis' journey from tlie nearest scientific library. 



Tlie present investigation was undertaken with the object of sett- 

 ling, jf possible, the much discussed question of the morphology of the 

 islets of Langerhans. Our work has been in the directions of comparative 

 anatomy and physiology. Many of our results have been in direct 

 confirmation of those of Dale and others, while we have been able to 

 add some new facts, and have reviewed a large part of the whole 

 subject from a widely comparative standpoint. We hope that what 

 we have been able to contribute will do much to place at least some 

 aspects of the question outside the pale of controversy. 



Into ilie question of the physiological significance of the islets of 

 Langerhans we have not entered at all fully, being convinced that a 

 necessaiy first step towards the elucidation of the problem is the solution 

 of the purely morphological question. We may say at the outset that 

 all the evidence we have to put forward is in favour of the views 

 held by Laguesse and Dale. 



We have, like Dale, employed the method of injecting secretin to 

 cause exhaustion of the pancreatic tubules, and carefully compared the 

 condition of the pancreas with that of the normal (resting) organ. The 

 animal employed for this purpose has been the dog. 



We have also examined the pancreas of animals after a period 

 of inanition, and, further, after their restoration to a normal condition. 

 The animals employed under this category of experiment have been 

 dogs, cats, pigeons and frogs. 



Our comparative studies have included a careful investigation into 

 the noimal structuie of the pancreas in the following animals: 



Mammals. Dog, cat, badger, ox, rabbit, guinea-pig, chipmunk 

 mouse, bat. 



Pjiids. Pigeon, duck, s])ai'iow. 

 Iteptiles. Chrysemys jncta, Kinosternon jie.nnsylvanicum. 

 .\iiiphil)i;nis. R(tii<i temporaria (rsriilcnhi'^). 

 /'/(■fimi 1 1) il (//ìifivnsiis'. 



