STUDIES ON THE PANCREAS OF THE GUINEA PIG 325 



without cell division, by experimental methods, and that there 

 is a corresponding return to the normal after the experimental 

 cause of the increase is withdrawn. Both of these methods have 

 been employed by Dale and by Vincent and Thompson with posi- 

 tive results. Of the value of these results it is impossible without 

 further experimentation to judge, nor is it possible with the data 

 given to repeat the experiments, for the authors in question nei- 

 ther give protocols of their experiments nor any indications as to 

 what may be their conception of the normal range of variation 

 in the number of islets in the pancreas of any of the species exam- 

 ined. Accordingly it has been my purpose to test the question 

 as to the possibility of influencing the number of islets in the pan- 

 creas by secretin stimulation, and inanition, by methods less open 

 to critical objection than these employed by Dale, Vincent and 

 Thompson, though I have been unavoidably ignorant of the 

 exact methods employed and the precautions observed by these 

 authors. 



1. Effect of secretin stimulation on the number of islets of Langer- 

 hans in the pancreas of the guinea pig 



In beginning experiments to determine the effect of secretin 

 stimulation on the number of islets of Langerhans in the pancreas 

 of the guinea pig it was necessary first to determine that the pan- 

 creas of the guinea pig responded sufficiently to secretin injections 

 to make it a good experimental animal. It will be recalled that 

 Bayliss and Starling ('03) showed that the pancreas of the rabbit 

 secreted slowly but continuously, and that the rate of secretion 

 was only slightly accelerated by the intravenous injection of 

 secretin. It might for this reason be urged that the guinea pig, 

 being also a herbivorous animal, would exhibit the same charac- 

 ters, and that therefore the pancreas might be expected constantly 

 to show the high islet content which, according to Dale, Vincent 

 and Thompson goes with a high degree of secretory activity. 

 In my counts of normal animals and experimental controls I 

 have been careful to guard against this objection by securing a 

 cessation of secretion by means of heavy doses of atropine sul- 



