240 Herrinor 



o 



100 mm. body length the male pancreas is rather heavier than the female. 

 For the reasons already stated it is doubtful how far these figures may be 

 regarded as correct. There is sufficient evidence, however, to support 

 Kojima's work, and to substantiate the fact that thyroid-feeding brings 

 about a great hypertrophy of the pancreas in both sexes. 



Histologically the increase of size of the pancreas appears to be due 

 to an increase in the size and number of the alveoli. It is difficult to 

 determine whether there is an increase in the islets of Langerhans. In 

 the pancreas of the thyroid-fed cat the islets of Langerhans are more 

 prominent than usual, and I have long been in the habit of giving prepara- 

 tions of pancreas from thyroid-fed animals to the histology class, because of 

 this prominence of the islets. 



5. The Liver. — The weight of the liver shows great variations in my 

 series of rats, but in all the control animals, male and female, the liver 

 weighs considerably less than that of the Wistar rat of the same body 

 weight or body length. The animals reared in this laboratory have much 

 lighter livers than the animals on which Donaldson's tables are based. 

 In my series, too, the liver is relatively heavier in the female than it is 

 in the male, a feature also shown in the Wistar Institute rats, but less 

 pronounced in them than it is in the rats reared in this laboratory. In 

 Hoskins' series the male liver is relatively larger than the female liver, 

 but both are lighter, except in j'oung males, than Donaldson's figures. 



Thyroid-feeding increases the weight of the liver, but not to such an 

 extent as is found in the organs already detailed. The liver of the male 

 animals shows an average increase of 45 per cent, per unit body weight, 

 and the liver of the females an average increase of 31 per cent. Measured 

 per 100 mm. body length, the increase is 40 per cent, in the males and 

 36 per cent, in the females. The increase in the males is largely helped 

 by the last rat of the series, which has an enormous liver. The averages 

 of the liver weights in the thja-oid-fed animals, male and female, 

 approximate verj'' nearly to the figures given by Donaldson as normal. 

 Hoskins obtained an enlargement of 6"4 to 24"4 per cent, of the livers 

 of male rats, and of 26 "7 to 30"5 per cent, of the livers of female rats. 

 as a result of thyroid-feeding'. Mv figures denote a larger increase in 

 the male, but approach Hoskins' figures for the percentage increase in 

 the female. The hj^pertrophy is only excessive in the case of the one 

 rat mentioned. No. 7 of Table lY., a rat which received the most thyroid. 



The enlargement of the liver found in the thyroid-fed animals is 

 probably not incompatible with Hoskins' explanation that it is due to 

 increased metabolism. The animals fed on thyroid ate more food than 

 the controls, and in some of them the increased food intake was verv 

 pronounced. In all the thyroid-fed animals in which a special examina- 

 tion was made there was an absence of glycogen from the liver, whereas 

 in the control animals glycogen was abundant. Cramer and Krause (3) 

 described the disappearance of glycogen from the livers of thyroid-fed 



