28 PRESIDENT’S ADDRESS, 
thus influenced, as are the skin-glands which secrete sweat. And by the 
action of the nervous system upon the skin-glands, together 
Regulation of with its effect in increasing or diminishing the blood- 
bc Foca i supply to the cutaneous blood-vessels, the temperature of 
our blood is regulated and is kept at the point best suited 
for maintenance of the life and activity of the tissues. 
The action of the nervous system upon the secretion of glands is 
strikingly exemplified, as in the case of its action upon the heart and 
blood-vessels by the effects of the emotions. Thus an 
Effects of emotion of one kind—such as the anticipation of food—will 
eee cause saliva to flow—‘ the mouth to water’; whereas an 
emotion of another kind—such as fear or anxiety—will stop 
the secretion, causing the ‘ tongue to cleave unto the roof of the mouth,’ 
and rendering speech difficult or impossible. Such arrest of the sali- 
vary secretion also makes the swallowing of dry food difficult: advan- 
tage of this fact is taken in the ‘ ordeal by rice’ which used to be 
employed in the East for the detection of criminals. — 
The activities of the cells constituting our bodies are controlled, 
as already mentioned, in another way than through the nervous 
system, viz., by chemical agents (hormones) circulating in 
the blood. Many of these are produced by special 
Regulation by ; ¥ 
chemical glandular organs, known as internally secreting glands. 
a dele The ordinary secreting glands pour their secretions on the 
Internal exterior of the body or on a surface communicating with 
secretions. the exterior; the internally secreting glands pass the 
materials which they produce directly into the blood. In 
this fluid the hormones are carried to distant organs. Their influence 
upon an organ may be essential to the proper performance of its func- 
tions or may be merely ancillary to it. In the former case removal 
of the internally secreting gland which produces the hormone, or its 
destruction by disease, may prove fatal to the organism. This is the 
case with the suprarenal capsules: small glands which are 
adjacent to the kidneys, although having no physiological 
connection with these organs. A Guy’s physician, Dr. Addison, in 
the middle of the last century showed that a certain affection, almost 
always fatal, since known by his name, is associated with disease of 
the suprarenal capsules. A short time after this observation a French 
physiologist, Brown-Séquard, found that animals from which the supra- 
renal capsules are removed rarely survive the operation for more than 
a few days. In the concluding decade of the last century interest in 
these bodies was revived by the discovery that they are constantly 
yielding to the blood a chemical agent (or hormone) which stimulates 
the contractions of the heart and arteries and assists in the promotion 
of every action which is brought about through the sympathetic nervous 
Suprarenals. 
