88 ROYAL SOCIETY OF CANADA 
cartilages, the larynx, and the medial coats of the arteries. Indeed we 
hardly grow up before we begin to die, for, as Klotz has shown, the 
majority of aortas of persons above thirty-five years of age show calca- 
reous deposits. Both sets of phenomena are constant accompaniments 
of life processes, are inevitable, and, physiological. At times, however, 
a deposit of lime salts occurs in such amounts, and so out of the natural 
order of events as to be distinctly abnormal. This is found, to make 
a broad generalization, particularly where tissues are dead or dying. 
Thus we meet with it in old inflammatory foci, notably in tuberculosis: 
in the case of serous exudates: in the arteries in arteriosclerosis; in 
thrombi; in calculi; in parasitic cysts; in tumours, to mention only 
some. But this by the way. 
We pass on to a phase of the subject which is to us, for the purpose in 
hand, of the chiefest importance, and one that in its latest developments 
is of absorbing interest. I refer to the part played by the ductless 
glands. 
So far as we are aware at present, the amount of calcium in the cir- 
culating blood in conditions of health is fairly constant within certain 
narrow limits, with the two exceptions above noted. This implies a 
regulating mechanism and this we find in certain of the ductless glands, 
notably the thyroid and parathyroids, the pituitary body, and the 
genital glands (ovaries and testes), all of which have been shown a 
notable influence over the processes of growth and development, includ- 
ing calcium metabolism. So striking is this influence that, just as the 
old anatomists were accustomed to refer to the three organs, heart, brain 
and lungs, as “the tripod of life,” I have been accustomed to think of 
the glands in question as “the tripod of growth.” This conception I 
have rendered graphic in the diagram (vide p. 89), which I have made 
use of before.! 
Not only are these glands mutually related one to the other in all 
possible combinations and permutations, but on their concerted action 
and balanced function normal development, and even existence itself, 
are dependent When one is diseased, also, we have the others exhibit- 
ing vicarious activity, a good illustration of what pathologists speak of 
as “the law of compensation.” To illustrate what I mean. 
Relationships between the pituitary body and the thyroid:— 
(1). Both organs are highly vascular, and contain both colloid and 
iodine. 
(2). After thyroidectomy or atrophy of the thyroid there is a com- 
pensatory hypertrophy of the pituitary. 

* Adami and Nicholls, Principles of Pathology, Vol. 2; 1909; 707., Lea and 
Febiger, Phila. 
