on the characters of eunuchs and capons, as well as spayed female
animals, he formulated a conception of sexual secretions absorbed
into the blood, settling the male or female tint of the organism and
setting the seal upon the destiny of the individual. Thus he must be
donated the credit of anticipating the most modern doctrine on the
subject.

The generation after him witnessed the triumph of the cell as the
recognized unit of structure of the tissues, the brick of the organs.
It was soon found that the cells of the more familiar glands, like
the sweat or tear glands, resembled the cells of the more mysterious
structures named the thyroid in the neck, or adrenal in the abdomen,
of which the function was unknown. What had hitherto prevented
classification of the latter as glands was the fact that they
possessed no visible pathways for the removal of their secretion. So
now they were set apart as the _ductless_ glands, the glands without
ducts, as contrasted with the glands normally equipped with ducts.
Since, too, they were observed to have an exceedingly rich supply of
blood, the blood presented itself as the only conceivable mode of
egress for the secretions packed within the cells. So they were also
called the blood or vascular glands.

The names which became most popular were those which represented a
contrast of the glands with the ducts, conveying their secretion to
the exterior, as the glands of EXTERNAL SECRETION and the glands
without the ducts, the secretions of which were kept within the body,
absorbed by the blood and lymph to be used by the other cells, as
the glands of INTERNAL SECRETION. How different these two classes
of glands are may be realized by imagining the existence of great
factories manufacturing food products, which would diffuse through