products to the blood. He did not, however, discover the action of such
products on other parts or functions of the body. Brown-Sequard, in his
address before the Medical Faculty of Paris in 1869, was the first to
suggest that glands, with or without ducts, supplied special substances to
the blood which were useful or necessary to the normal health, and in 1889
at a meeting of the Societe de Biologie he described the experiment he had
made upon himself by the injection of testicular extract. This was the
commencement of organotherapy. Since that time investigation of the more
important organs of internal secretion--namely, the gonads, thyroid,
thymus, suprarenals, pituitary, and pineal bodies--has been carried on
both by clinical observation and experiment by a great number of
physiologists with very striking results, and new hormones have been
discovered in the walls of the intestine and other organs.

Here, however, we are more especially concerned with the gonads and other
reproductive organs. A great deal of evidence has now been obtained that
the influence of the testes and ovaries on secondary sexual characters is
due to a hormone formed in the gonads and passing in the blood in the
course of the circulation to the organs and tissues which constitute those
characters. The fact that transplanted portions of testes in birds (cocks
and drakes) are sufficient to maintain the secondary characters in the
same condition as in normal individuals shows that the nexus between the
primary and somatic organs is of a liquid chemical nature and not
anatomical, through the nervous system for example. Many physiologists in
recent years have maintained that the testicular hormone is not derived
from the male germ-cells or spermatocytes, but from certain cells between
the spermatic tubuli which are known as interstitial cells, or
collectively as the interstitial gland.

The views of Ancel and Bouin, [Footnote: _C. R. Soc. Biol., iv._]