452 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
to one side of the face, and such local manifestations are not un- 
common. It is by a variation in the sensitiveness of the local re- 
cipient that we have an explanation of the endless variety to be found 
in the relative development of racial and individual features. 
Some 10 years after Starling had formulated the theory of hor- 
mones, Prof. W. B. Cannon, of Harvard University, piecing together 
the results of researches by Dr. T. R. Elliott and by himself on the 
action of the suprarenal glands, brought to light a very wonderful 
hormone mechanism—one which helps us in interpreting the action 
of growth-regulating hormones. When we are about to make a 
severe bodily effort it is necessary to flood our muscles with blood, 
so that they may have at their disposal the materials necessary for 
work—oxygen and blood sugar, the fuel of muscular engines. At 
the beginning of a muscular effort the suprarenal glands are set 
going by messages passing to them from the central nervous system; 
they throw a hormone—adrenalin—into the circulating bleod, which 
has a double effect; adrenalin acts on the floodgates of the circula- 
tion so that the major supply of blood passes to the muscles. At the 
same time it so acts on the liver that the blood circulating through 
that great organ becomes laden with blood sugar. We here obtain 
a glimpse of the neat and effective manner in which hormones are 
utilized in the economy of the living body. From that glimpse we 
seem to obtain a clue to that remarkable disorder of growth in the 
human body known as acromegaly. It is a pathological manifesta- 
tion of an adaptational mechanism with which we are all familiar. 
Nothing is better known to us than that our bodies respond to the 
burden they are made to bear. Our muscles increase in size and 
strength the more we use them; increase in the size of our muscles 
would be useless unless our bones also were strengthened to a corre- 
sponding degree. A greater blood supply is required to feed them, 
and hence the power of the heart has to be augmented; more oxygen 
is needed for their consumption and hence the lung capacity has to 
be increased; more fuel is required, hence the whole digestive and 
assimilative systems have to undergo a hypertrophy, including the ap- 
paratus of mastication. Such a power of coordinated response on the 
part of all the organs of the body to meet the needs of athletic train- 
ing presupposes a coordinating mechanism. We have always re- 
garded such a power of response as an inherent property of the living 
body, but, in the light of our growing knowledge, it is clear that we 
are here dealing with an hormonic mechanism, one in which the 
pituitary gland is primarily concerned. When we study the struc- 
tural changes which take place in the first phase of acromegaly (see 
Keith, Lancet, 11, p. 993, 1911; i, p. 305, 1913) we find that not only 
are the bones enlarged and overgrown in a peculiar way, but also 
