Though the thyroid is the supreme energizer, life is incompatible with a certain excess of it.  Death can be produced by successive daily injections of its internal secretion.  But it has, besides the energizing effect, certain formative and nervous influences equally marvelous.  As illustrations, there are the cases of thyroid deprivation in human beings, cretinism and myxedema, as well as those in which it is believed there occurs an excess of the thyroid secretion in the blood and tissues, the condition of hyperthyroidism.

CRETINISM AS THYROID DEFICIENCY

Not that there is any arresting contrast of startling difference between the phenomena presented by different species.  The younger the animal, the grosser the morbid symptoms witnessed.  The animal fails to grow.  The bones and cartilage, except of the skull, fail to develop.  The abdomen projects and becomes large and flabby.  The sex organs atrophy.  There is sterility.  Pregnant rabbits abort, hens produce very small eggs or none at all.  These are the results of removing the thyroid in animals.

Apathetic, indifferent, dirty, awkward, apparently idiotic, describe the human cretins.  Their skin is rough and coarse, peeling in sheets.  In some it is considerably knarled and creased as in the aged, and in others swollen, hard and resistant.  The hair becomes shaggy and rough, losing all luster, and tends to grow irregularly and fall out.  The temperature becomes subnormal and an anemia supervenes.  There is a distinct reduction in the resistance to infections and intoxications.

Cretinism in the human is a condition in which the burning taper we call Life flickers and smoulders and smokes.  Thirty years ago it was an example of the most hopeless idiocy.  Whole populations were afflicted with it.  But neither man of science, nor bigot-fanatic, assured by the Divine Confidence of its meaning as a visitation, believed it could be modified an iota.  Today, that inept word “cure” may be applied to our power of attack upon it, provided it is permitted to attack early enough.  Modification, in the direction of the most surprising betterment, is the miracle that has been wrought.

The history of a cretin runs somewhat as follows:  A baby is born, which in all appearances seems normal.  Perhaps the nose is a trifle squatter than even the average new-born’s flat nose.  There may also be abnormal sleepiness, greater even than that of the normal baby in the first month or two in that there is no spontaneous awakening from the coma for food.  But in most cases this is put down to normal variability, or maybe to that limbo of all a baby’s troubles:  weakness.  After some months, it is noticed that the infant is failing to grow at the normal rate, either physically or mentally.  Examination at this time reveals a curious thickening of the dental ridges.  Then the tongue takes the centre of the scene, by becoming unusually thick and prominent, to the point of projecting beyond the mouth at all times, and interfering with breathing, when the infant is in a recumbent position.