THYROIDECTOMY AND THE METABOLISM 51 



perform the functions of the thyroid just as they resemble Effects of 

 it in structure. But I do not believe that this question tomy^ary in 

 of the remaining parathyroids is the whole truth. 

 Herbivora have less need of the thyroid than other 

 mammals, such as the carnivora. It may be because 

 the diet is different, but I feel sure it is also due in some 

 measure to the variations in the structure and func- 

 tion (or degrees of function) seen in the other hormono- 

 poietic organs. I have already alluded to the differences in 

 structure between the ovaries of rodents and those of the 

 higher mammals. If, however, we take cats and remove 

 their thyroids, many die in a few days, usually with con- 

 vulsions. In these cases it is probable that the immediate 

 result is due to the removal of the whole thyroid apparatus 

 (thyroparathyroid). Some cats, nevertheless, may survive 

 the operation for a long period of time ; and in all these 

 cases one can demonstrate the removal of the whole 

 thyroid together with the internal parathyroids, one of 

 which is embedded in each lobe of the thyroid. In 

 these animals, therefore, the true effects of thyroid in- 

 sufficiency may be obtained. Further, it has been stated 

 by Stanley Kent 1 and confirmed by Hick and myself 2 , Castration 



that castration minimizes the effect of thyroidectomy. ffto'f thy- 



The number of cats in my experiments in which the 

 metabolism after thyroidectomy was investigated fully 

 was small, for, as already stated, many died too soon 

 for the metabolism, as represented by the urinary 

 excretion, to be estimated. The record of one non- 

 pregnant cat (table III, cat no. 1) which was destroyed 

 two and a half months after operation, has been selected 

 as typical. Other experiments were complicated by the 

 cats having had kittens shortly before operation, and in 

 consequence the figures obtained from them did not 

 appear to be suitable for averaging with those from the 

 uncomplicated cases. 



1 Kent, S., Journ. Physiol. (Proc. Physiol. Soc.), 1894, vol. xv, 

 p. 18. 



2 Bell, W. Blair, and P. Hick, Brit. Med. Journ., 1909, vol. i, 

 p. 517. 



