186 



Scientific Proceedings (54). 



hyperplasia, there ought to be no fetal goiters in the case of mothers 

 with normal thyroid or with colloid goiters; and the fetal goiters 

 of mothers with active hyperplasia ought to diminish after birth. 



1. Results in Dogs. — During intrauterine life the body in- 

 creases in weight faster than the thyroid gland so that the ratio of 

 the weight of the thyroid to the body weight becomes gradually 

 larger. But in the case of mothers with normal (or nearly normal) 

 thyroids, the ratio of thyroid to body weight is always greater in 

 the mother than in the pups; in the case of mothers with colloid 

 glands the ratio may be greater in the pups than in the mother 

 while in the case of mothers with thyroid hyperplasia the ratio 

 may be the same, or it may be higher or lower, depending on the 

 degree of hyperplasia of the maternal thyroid. 



The newborn of mothers with active hyperplasia have invari- 

 ably much larger thyroids than the pups of normal mothers, but 

 the thyroids of the former do not exhibit any greater degree of 

 differentiation toward adult structure. It would thus seem that 

 the conditions causing thyroid hyperplasia in the mother lead in 

 the fetus to excessive growth of the thyroid rather than to specific 

 thyroid differentiation. 



In the case of mothers with colloid goiter the thyroids of the 

 pups are on the whole of the same size as in the pups born of 

 normal mothers. A few thyroid ratios may be cited for illustra- 

 tion. 



On the whole, the relative weight of thyroids in dogs, both 

 adult and newborn, is large in comparison with that in cats. 

 There may be considerable variation in the thyroid : body weight 

 ratio in pups of the same litter. We have not been able to deter- 

 mine whether this is due to primary difference in the ova or to the 

 varying factor of accessory thyroids. 



2. Results in Cats. — Active hyperplasia or colloid goiter has 

 not yet been found in our pregnant cats. But there is some vari- 

 ations in relative bulk of thyroid tissue. Thus the extremes of 

 thyroid-body weight ratio are 1-4,680, and 1-16,000 respectively. 



V. Normal thyroid 



X. Colloid goiter 



III. Thyroid hyperplasia 



Ratio of thyroid to body weight. 



Mother. Pups. 

 . . 1-6,600 1-3,000 

 . . 1-1,300 1-4,200 

 ..1-1,100 I- 480 



