finite like our knowledge of the thyroid
and the pituitary.

There is evidence that the thymus is involved in the health and
efficiency of muscle cells and muscularity. Certain tumors of the
thymus, presumably destructive of the gland substance proper, and
thus cutting off its secretion, are accompanied by a singular muscle
weakness and atrophy of the muscle cells, entirely out of proportion
to the general damage suffered by the other cells of the body when
affected by the poison of a malignant growth. Also, the thymus has
been discovered diseased in certain mysterious progressive muscular
wastings. A remarkable fatigability of muscles, which appears after
the slightest exertion, is a feature. The feeding of thymus has caused
muscle cramps which apparently depends upon an increased excitability
of the muscle nerve endings.

Feeding of thymus to some of the lower creatures of the animal kingdom
will completely hold up differentiation. Take the unfolding of the
specialized tissues and organs which transform the tadpole into the
frog and the chrysalis into the butterfly. A tadpole kept supplied
with enough thymus in a nutrient medium will swell into an
extraordinary giant tadpole, but will not change into a frog.
Recently, this experiment has been contradicted. Yet this effect
corresponds to the conception of its importance in childhood as a
retardant of precocity, physical and mental. Clinical observations
emphasize that in childhood it is the chief brake upon the other
glands of internal secretion which would hasten development and
differentiation, checking them perhaps for a given time and so
profoundly influencing growth.

THE PINEAL

The pineal is another gland which has been credited with similar
abilities and a like holding-the-reins-tight-in-childhood function
among the cells. Like the thymus, it has been supposed one of the
distinctive organs of childhood and to die with it. Generations of
anatomists solemnly asserted, repeating each other's mistakes with the
aplomb of the historians who declare that history repeats itself, that
the pineal body was a useless, wastefully space consuming vestige of a
once important structure. That was the view in that century of grandly
inaccurate assertions, the nineteenth. Not that they relegated it with
that statement to the limbo of the dull and the uninteresting. Quite
the contrary. They conferred upon it a distinguished romance and
mystery by identifying it as the last h