280 ' Kojima 



the small cells are especially abundant in the small alveoli. Most 

 of the nuclei are large ; there is, however, considerable variation in 

 size (3'7/x to 11/^). The nuclei of the small cells are smaller than 

 the rest, and stain more deeply. The nucleoli generally are large, 

 and with Mallory are stained red, the nuclei being coloured blue. 

 Most contain abundant coarse chromatin granules. Some of the cells 

 show mitotic figures, but these are not very numerous. Portions 

 of the pancreas, consisting usually of isolated lobules, are here and 

 there seen to be wholly formed of small cells which have lost their 

 typical alveolar arrangement and exhibit signs of having recently 

 undergone proliferation ; indeed, some of them still exhibit mitoses ^ 

 (see Plate II.). 



Zymogen granules are far less numerous than in the normal 

 pancreas. These granules, which are stained very distinctly by 

 Mallory, form a red mass in the ordinary cells, but in the smaller 

 cells they are very scanty and are scattered in the cytoplasm, not 

 massed together. Vacuoles, some quite large, are present in many of 

 the alveolar cells. Vacuolation may also be seen in some of the cells 

 of the islets of Langerhans. 



In rats Nos. 22, 23, 24 (group C) the changes in the pancreas 

 are similar to those just detailed. The controls (Nos. 16 and 18, 

 group A) show normal appearances. 



Summary. — After thyroid feeding with intermission, and also if the 

 dose of the thyroid be increased, the pancreas is larger in proportion to the 

 body-weight than in the controls. It shows, besides the ordinary alveoli, 

 others which consist entirely of small cells not regularly arranged into 

 alveoli and containing very little zymogen. A certain number of the 

 alveolar cells show mitoses, and many of them have large vacuoles. 



A second thyroid feeding following on the first after a certain interval 

 appears to produce less effect than the first. 



Effect of Thyroid Feeding on the Weight of the Pancreas. 



The weight of the pancreas was examined in the three groups which 

 have just been noticed (Table VIIL). In order to determine the weight 

 the pancreas was entirely freed from mesentery with the assistance of 

 a lens, and was weighed in all cases at as nearly as possible the same 

 degree of moisture. In order to compare with the weights obtained in 

 these experiments, the pancreas of nine other full-grown normal male 

 rats were also weighed (see Table IX.).^ These tables show a distinct 

 increase of pancreas-weight relatively to body-weight in the thyroid-fed 

 animals. 



The increase in size of the pancreas which is produced by the thyroid 

 feeding is illustrated in the photographs shown in fig. 14. 



1 Mitoses are seen in the rat's pancreas as long as tliree days after thyroid feeding has 

 been stopped. 



- The weight of the pancreas was not taken in any of the early experiments. 



