es. The researches of Steinach and others have made the
old theory untenable and demonstrate that the semen is a mixture from
three distinct sources; that the testicles secrete their contribution
to the semen only during sexual stimulation; while the seminal
vesicles secreting their products continuously become periodically
filled and distended.

Let us inquire regarding the function of this alkaline albuminous
secretion from the vesicles and prostate. For what purpose does Nature
prepare such a secretion? The spermatozoa frequently remain several
days in the organs of the female before the ovum is found and
fertilized. During these several days the spermatozoa are exerting no
small amount of energy in their vigorous flagellate movement. For such
an expenditure of energy they must receive nourishment and
stimulation. The nourishment is supplied by the albumin and proteid of
the vesicular and prostatic secretions. The stimulation is supplied by
the salts also secreted by these glands. The recent researches of Loeb
and others have demonstrated the importance of mineral salts in
stimulating the activity of living cells. One can cite no better
example of this stimulant action than the influence of these
vesicular and prostatic salts upon the activity of the spermatozoa.

The vesicles and prostate may be looked upon as the commissariat of
the army of spermatozoa; the vesicles accumulating a stock of supplies
to be drawn upon at short notice; the prostate representing a factory
where a considerable quantity of supplies can be prepared at short
notice.

This _periodic distention of the seminal vesicles_ is a matter of very
considerable hygienic importance and must be thoroughly understood by
every young man who would lead a normal sexual life.

These organs in common with all other organs of the body are supplied
with two sets of nerves, one set passing away to the spinal cord and
carrying messages which indicate the condition of the organ or the
presence and character of any local stimulus; the other passing away
from the spinal cord to the organ and carrying secretory and motor
impulses. The secretory impulses are more or less continuous and as a
result, these glands secret continuously and become periodically
distended as described above. The motor impulses pass to the muscles
within the walls of the vesicles, causing a strong spasmodic
contraction of these muscles at the moment of emission of semen, thus
throwing the