90 ROYAL SOCIETY OF CANADA 
Relationships between the thyroid, and the genital functions :— 
(1). The thyroid often manifests enlargement in girls, at or just 
before the first menstruation. 
(2). It becomes tumid in many girls and women during the 
menstrual periods. 
(3). It enlarges during pregnancy. 
(4). In cretinism, a disease due to lack of thyroid secretion, there 
is a condition of sexual infantilism. 
(5). Thyroid extract has been given with benefit in cases of ame- 
norrhcea due to debility. 
If, to use an arithmetical expression, we attempt to reduce the 
functional activity of these three organs (regarding the testes and ovaries 
as homologous and functionally similar), to a common denominator, we 
find it in their influence over growth and development, in which the 
formation of bone plays not the least part. Referring to the latter point 
entirely, the observed facts are striking and significant. In cretinism, 
the result of thyroid insufficiency, the bones are stunted and ossification 
is delayed. Certain tumours and cysts of the pituitary lead to great 
overgrowth of the bones as in giantism and acromegaly. Castration 
in the male, performed before puberty, results in the formation of a 
feminine type of larynx and an increase in the length of the lower extre- 
mities. The removal of the ovaries has been known to cure osteo- 
malacia, a disease in which the lime salts are gradually withdrawn from 
the bones, which in consequence become brittle, soft and deformed. 
Without being dogmatic on the point, it would seem extremely 
probable, on the ground of recent experimental work, that the explan- 
ation of these phenomena is to be looked for, at least to a large extent, 
in the influence which these glands exercise over calcium metabolism. 
The proofs are not yet absolutely final but all the available evidence 
points in this way. 
What we know positively about it amounts to this. The brilliant 
experimental work of MacCallum and Voegtlin' has shown that extir- 
pation of the parathyroids is followed by a remarkable increase in the 
elimination of calcium salts, leading to the production of tetany, 
convulsions and death. This result could be prevented by the exhi- 
bition of lime salts in sufficient amount. They suggest that the lime 
acts by neutralizing potassium salts, for the symptoms are exaggerated 
and the good effects of calcium prevented by the latter agents. Very 
recently Franchini? has discovered that the exhibition of pituitary 

* MacCallum and Voegtlin, Johns Hopkins Hosp. Bulletin, 19; 1908; 191. 
? Franchini, Berliner klinische Wochenschrift, 47; 1910; 613, 670, 719. 
