128 Proceedings of the Royal Physical Society. 
its antecedent proportions, the bald head grows its hair, the 
fog is dispelled from the brain, and the mental faculties 
resume their activities. In the cretin, if a young child, 
what was little more than a sentient vegetable becomes 
active and lively, amusing itself as other children, grows 
in body, develops a mind like other children, and, if I may 
say so, presents the potentialities of an immortal soul. 
In these cases there is no doubt as to cause and effect, and 
you will agree with me that such a correlation suggests many 
curious thoughts. The destruction of a gland, thought to be 
useless, leads to physical conditions which are strikingly 
apparent, and are allied with mental phenomena startling 
both in degree and in kind; and all these then removed by 
regularly swallowing small quantities of the gland from the 
sheep corresponding to the one destroyed in the human 
being. 
The inference is, of course, unavoidable that this gland 
elaborates a substance which passes into the blood, is carried 
to brain and other tissue, and is absolutely essential for 
the maintenance by these of their normal functions. The 
steps of this discovery were made by men engaged in the 
observation and investigation of disease,and pure physiology 
and biology owe it to medicine. The discovery has thrown 
a new light on vital processes, for the glands, the functions 
of which were known, were glands whose secretions in the 
main were connected very directly with digestive processes, 
while some others were related to blood-corpuscle formation. 
The function of the thyroid showed that there were organs 
whose secretions were essential to the well-being of certain 
tissues, and that they cou'd, of course, only reach these 
tissues, and be uniformly distributed to them, by the secre- 
tion entering the blood; and this could only be attained in 
the ductless glands by passing through the lymphatic 
vessels. The influence of this particular secretion, which is 
perhaps the most attractive, is the effect its absence has upon 
the brain—an effect altogether surprising and unexpected, 
as is also the further fact that this potent substance can be 
added to the blood by the somewhat coarse method of intro- 
ducing it artificially into the stomach, and that the stomach 
