Fig. 82. — Differential effect of thyroid removal upon the growth of various 



organs in the male Albino rat. 



The curves indicate the amount of growth made by an organ, represented as a percentage of the 

 amount of growth made by the same organ in unoperated controls. For each organ there are 6 points, 

 representing operations carried out at ages from 23 to 100 days ; all the 6 series were allowed to 

 grow until 150 days of age before final organ-size was determined. In all graphs the heavy line 

 represents the curve for body-weight in thyroidectomized animals. In all cases the effect, relative 

 to the control, is greater in animals operated later. 



(A) Organs of resistant type : eyes, spinal cord, brain. All are less reduced than body-weight. 



(B) Organs of sensitive type : heart, lungs. The heart in particular is more reduced than body- 

 weight. In animals operated at 100 days of age, both heart and lungs actually lose weight (negative 

 increment). 



185 



