terminate in rounded coils, enveloped by a net-work of capillaries,
which supply the secretory glands with blood. It is estimated by Krause
that the entire number of perspiratory glands is two million three
hundred and eighty-one thousand two hundred and forty-eight, and the
length of each glandular coil being 1/16 of an inch, we may estimate the
length of tubing to be not less than two miles and a third. This
secretion has a specific gravity of 1003.5, and, according to Dr.
Dalton, is composed of

Water, 995.50
Chloride of Sodium, 2.23
Chloride of Potassium, 0.24
Sulphate of Soda and Potassa, 0.01
Salts of organic acids, with Soda and Potassa, 2.02
-------
1000.00

Traces of organic matter, mingled with a free volatile acid, are also
found in the perspiration. It is the acid which imparts to this
secretion its peculiar odor, and acid reaction. The process of its
secretion is continuous, but, like all bodily functions, it is subject
to influences which augment or retard its activity. If, as is usually
the case when the body is in a state of repose, evaporation prevents its
appearance in the _liquid_ form, it is called _invisible_ or _insensible
perspiration_. When there is unusual muscular activity, it collects upon
the skin, and is known as _sensible perspiration_. This secretion
performs an important office in the animal economy, by maintaining the
internal temperature at about 100° Fahr. Even in the Arctic regions,
where the explorer has to adapt himself to a temperature of 40° to 80°
below zero, the generation of heat in the body prevents the internal