The Action of Thyroid upon the Organs of the White Rat 239 



Among the female rats No. (5, Table VIII., shows kidneys weighing 

 20.SG grm. This rat received 01 grm. fresh thyroid for thirty-six days, 

 and has a body weight of 140 grm., and a length of 174 mm. Donaldson's 

 average for the kidneys of a female rat of this size is about 1-200 grm. 

 The kidneys of the thyroid-fed animal show an increase of weight amount- 

 ing to 61 per cent. 



The average increase in weight of the kidneys of the thyroid-fed 

 animals per 100 grm. body weight over that of the controls amounts to 

 106 per cent, in the males, and 63 per cent, in the females. Per 100 mm. 

 body length the increase is 100 per cent, in the males, and 70 per cent, in 

 the females. 



The kidneys of the normal rat are relatively heavier in the female than 

 in the male. The increased weight due to thyroid feeding is greater in 

 the male than in the female, but the males received more thyroid. The 

 increase of weight seems to be roughly proportional to the amount of 

 thyroid given. 



Hoskins with smaller doses obtained an increase in weight of the 

 kidneys varying from 33 to 46*3 per cent, in females, and from 40-4 to 

 44'4 per cent, in males. 



Histologically the enlarged kidneys of thyroid-fed animals show an 

 increase in the size of the tubules and a looser texture of the kidney 

 generally. In the extreme enlargements there is a decided increase in 

 the amount of connective tissue in the kidney. 



4. The Pancreas. — No figures relating to the weight of the normal 

 rat's pancreas are given in Donaldson's memoir. Hoskins describes an 

 increase in the weight of the alimentary canal, including pancreas and 

 mesentery, as the result of thyroid-feeding. Kojima (16) found evidences 

 of greatly stimulated growth in the abundance of karyokinetic figures in 

 the pancreas induced by thyroid-feeding. 



The measurements of the weights of the pancreas given in this paper 

 are probably not quite correct. It is ditficult to distinguish some of the 

 rats' pancreas from fat, and being a diffusely spread organ it is mixed with 

 a good deal of fat and connective tissue. The pancreas was carefully and 

 widely removed, spread out on a dark surface, and as much fat, lymph 

 glands, and mesentery removed as possible. This is less difficult in the 

 thyroid-fed animals, in which there is little or no fat. The weights in both 

 groups of animals are probably in excess of the true value, but rather more 

 so in the normal animals than in the thyroid-fed. 



Thyroid-feeding gives rise to a large hypertrophy of the pancreas in 

 both sexes. The average figures show an increase in weight of 111 per 

 cent, in the male thyroid-fed animals, and an increase of 80 per cent, in 

 the female thyroid-fed rats. Per 100 mm. body length the increase is 

 104 per cent, in the males, and 87 per cent in the females. 



According to the figures recorded, the weight of the pancreas per 

 100 grm. body weight is rather greater in females than males, but per 

 VOL. XI., NO. 3. — 1917. 16 



