THE THYBOID GLAND AND ITS DISEASES 239 



organs is dependent on the functional integrity of the thyroid. Sexual 

 intercourse in both sexes increases the activity of the gland, and it is 

 likely to swell in consequence. Married men under forty years of age 

 are on the whole of better physique than the unmarried, a fact probably 

 partly depending on the maintenance of thyroidal activity which marriage 

 assures. The same applies to women. (McCarrison.) 



There is considerable uncertainty in connection with the relations 

 between the thyroid and the ovaries. It is stated that the ovaries exercise 

 an inhibitory action on the thyroid ; in fact, the latter becomes hyperactive 

 after castration, and there is an increase of colloid matter. This is the 

 cause, it is said, of the larger number of cases of exophthalmic goiter after 

 the menopause. (Gley.) 



It is possible that the relations of the thyroid to the organs of repro- 

 duction will be fully comprehended only when the part played by the 

 adrenal cortex is understood. 



The Relationship Between Thyroid and Parathyroid 



The earlier investigators looked upon the parathyroids as embryonic 

 thyroids and a belief in some kind of morphological and physiological 

 relationship between the two glands has persisted, in one form or another, 

 up to the present time. But for the past twenty years the majority of 

 authors have inclined to the view that the parathyroid is to be regarded 

 as an organ sui generis. The problem of thyroid and parathyroid re- 

 sembles in some respects that of adrenal body and chromaphil tissue. In 

 both cases we have to deal with two different kinds of tissues, of separate 

 embryological origin, and presenting marked divergencies in histological 

 and chemical characters. In both cases we see the two different tissues 

 coming together in such a way as to present, from an anatomical aspect a 

 single organ. It is not clear, from an a priori standpoint, whether we 

 ought to expect that the anatomical conjunction implies any kind of 

 physiological cooperation. In the case of the adrenal and the chromaphil 

 tissue there is very little evidence in favor of any physiological relation. 

 In regard to the thyroid and parathyroids the experimental evidence has 

 been somewhat contradictory. Jolly and the present writer, as well as 

 some other authors, have reported that on microscopical examination of 

 parathyroids left in situ after removal of the thyroid, an alteration in 

 structure had occurred. The parathyroids were said to have developed 

 vesicles resembling those of the thyroid. The experiments were carried 

 out upon dogs and cats. 



A recent series of experiments upon rabbits by Arnason and the 

 present writer does not lend support to the view that parathyroids left 

 Miind after thyroidectomy become converted into thyroid tissue. It is 



