266 Kojiina 



Pancreas (figs. 7, 8, and 9, and Plate I., B). — The pancreas is 

 pink in colour. The alveolar cells vary considerably in size, but 

 the alveoli are, on the whole, smaller than in the animals killed prior 

 to the addition of thj^roid to the diet. The nuclei, on the other hand, 

 are larger ; most of them measure from 7yu to lO^t. Tiie largest con- 

 tain coarse chromatin granules uniformly scattered within them, and 

 usually stain rather more darkly with hajmatoxylin than the rest. 

 Sometimes there is an enlarged nucleolus. Many of the alveolar 

 cells exhibit mitotic figures in various stages of karyo- 

 kinesis (fig. 8 and Plate I., B). These dividing cells are large; their 



Fig. 7.— Section of pancreas of rat (male) fed with an addition to the ordinary 

 diet of 1 grm. of dry ox-thyroid per diem during seven days. Microphotograph ; 

 magnified 90 diameters. Haematoxylin jjreparation. 



If this is compared with fig. 1, it will be seen that tlie gland has a more 

 compact a])pearance, and that the inner (zymogen) zone of the alveoli is smaller 

 than in the normal animal. Two islets are included in the field. 



cytoplasm is but little stained with lia3matoxylin, and shows no sharp 

 distinction between outer and inner zones. Paranuclei are some- 

 times observable in the cytoplasm near the nucleus. The cytoplasm 

 of the dividing cells is stained faintly blue by Mallory, whilst the 

 scanty and scattered zymogen granules and the paranuclei are stained 

 red. So numerous are the mitoses that in places a dozen or more are 

 visible within one field of the ordinary high power (GOO diameters) of 

 the microscope. 



The cells which exhibit mitosis are usually sharply outlined and 

 partially separated from the adjacent cells. They usually have a 

 spheroidal form. 



Many of the cells which are not undergoing mitosis are also large. 

 Their cytoplasm is but little stained with haematoxylin ; their nuclei, 



