The Action of Thyroid upon the Organs of the White Hat 243 



special action on the ovaries, but it is probable that their growth is to 

 some extent accelerated by the general change in the body produced by 

 hyperthyroidism. 



Histologically no essential alteration is found in the ovaries of the 

 thyroid-fed animals. 



10. The Uterus. — The uterus in my measurements includes the two 

 cornua and the Fallopian tubes to their attachment to the ovaries. The 

 lower end was separated by a transverse cut through the junction of uterus 

 and vagina. The line of junction is not very definite, but can be felt by 

 compressing it between finger and thumb. Slight deviations from the 

 junction do not materially affect the observed weight of the organ. No 

 data are available for comparison with my figures as far as I am aware. 

 The uterus shows extreme variations in weight. In none of the measure- 

 ments was there any sign of the uterus being in a period of restrus at the 

 time. All the animals were virgins. 



In the thyroid-fed rats the general impression formed was that the 

 uterus is distinctly retarded in development. A striking exception is 

 furnished by No. 6 rat. In this animal, which received O'l grm. of thyroid 

 for thirty-six days, the uterus is exceptionally large, weighing more than 

 those of five of the other animals added together. Even with the inclusion 

 of this organ the uteri of the thyroid- fed animals average 11 to 14 per cent, 

 less by weight than those of the control rats. With the exclusion of No. 6 

 rat and its control the weights of the uteri of the remaining six animals 

 average 162 per cent, less than those of the controls. 



Iscovesco noted a large hypertrophy of the uterus in rabbits treated 

 with thyroid material. There is no evidence in my figures of thia being 

 the case in rats except in the one instance mentioned. This animal was 

 the largest of the series, and had a large pituitary body and a moderately 

 large thymus. 



It is interesting to note that the small uterus is associated in my 

 series with a small pituitary body, and to some extent with a relatively 

 large thymus. There are exceptions, however, particularly with regard 

 to the thymus, and my figures do not bear out any satisfactory establish- 

 ment of a correlation between thymus and uterus. The correlation between 

 uterus and pituitary body is more striking. The normal variability of 

 the uterus is so great that these figures may have no special significance. 

 On the other hand, it is possible that in young animals thyroid may restrain 

 the development of the uterus indirectly by its action on the pituitary body. 

 Further observations are necessary on this subject. 



11. The Thyroids. — Measurements of the thyroids were only made 

 in the female animals of the series, but several have been made in males 

 since the tables given were drawn up. The thyroids of both males and 

 females were examined histologically. 



The normal weight of the thyroids is liable to considerable variations. 

 The o-eneral averase in the control animals is less than that of the Wistar 



