JStudiea on the Endocrine Glands 



285 



test in the urine gave a positive reaction from the second day of feeding 

 onwards. At the termination of the period the animals were killed. 



Pancreas. — Tiie alveoli are somewhat smaller than normal, and 

 although most of thf alveolar cells are fairly e(jual in size, a consider- 

 able number of small cells are included amtjngst them (fig. 15). The 

 nuclei vary in diameter from 'A7ju to 75/>c ; a few larger ones are seen 

 (10/u). The.se contain abundance of chromatin granules. Zymogen is 

 but scanty. Many cells exhibit mitosis, and a few show vacuolation. 



Summar}'. — These experiments make it evident that a much smaller 

 amount of added thyroid than that used in most of our experiments is 

 sufficient to cause the etiects on the pancreas which have been described as 

 characteristic of thvroid feedinor. 



Effects of Prolonged Feeding with Thyroid. 

 The effects of prolonged feeding were next investigated : accordingly, the 

 following experiments extended over a month. The material used, was 

 partly dry ox-thyroid, partly fresh sheep-thyroid. Four full-grown female 

 rats (non-pregnant) were separated into two groups, A and B, and fed with 

 rusk paste. To the food of A group 1 grm. of dry ox-thyroid per rat per 

 diem was added: to that of B group 4 grm. of fresh sheep-thyroid. The 

 experiment lasted from May 28 until June 2(5. From the fourth day of the 

 feeding one of the two rats of A group had marked diarrlujea, and all the 

 other animals of both groups suffered from slight diarrhcea. The appetite 

 in all was diminished, but after the second week gradually recovered. By 

 the end of the fourth week the animals were all healthy and showed no 

 special symptoms. They had also increased in weight, although they lost 

 in weight during the first period of feeding. They were killed on June 27. 

 The weights at different periods are given in Table X. 



Pancreas. — All the rats in this series of experiments show much 

 the same appearances in the pancreas. The alveoli are for the most 



