e general symptoms is caused by the fever, and how much by
the disease which is the cause of the fever.

The importance of high temperature having been recognized, it becomes a
matter of the gravest scientific and practical interest to determine the
method in which it is produced.

There are only two systems which bind the body together--namely, the
circulation and the nervous system. As fever is usually a universal
phenomenon, occurring simultaneously in every part of the body, it must
be produced either through the nervous system or by a poison in the
blood acting simultaneously on every tissue. Every physician knows,
however, that there are cases of fever in which there has been no
introduction of a poison into the blood: hence it follows that at least
sometimes fever must be produced by the nervous system.

This being so, the study of the influence of the nervous system upon
animal heat is naturally the next step in our investigation. Before
making this step it may be well to call to mind the fact that chemical
processes are usually accompanied either by the giving out or the
withdrawal of heat. Thus, the chemical actions which result when ice and
salt are mixed cause a withdrawal of heat, and a "freezing mixture" is
formed. When a candle is burnt, the oxidation of its constituents, a
chemical process, evolves heat. Oxidation is the great source of
artificial heat, and animal heat is chiefly generated by the same
process; in other words, animal heat is always the product of the
chemical movements of the body, and these movements are almost
exclusively of the character of oxidation. In the animal tissues a
lessened oxidation is equivalent to a lessened heat-production, and
_vise versa_.

If a large nerve be exposed in one of the lower animals, and a galvanic
current be sent through it for half a minute or more, the temperature of
the animal falls very decidedly; and if the irritation be repeated
several times at intervals, the diminution of the animal heat may amount
to several degrees. Galvanization of a nerve affects very powerfully the
circulation, and it has been believed that this derangement was the
cause of the lessened chemical movements. But the alteration of the
circulation is immediate, and ceases almost at once when the current is
broken, whereas the fall of temperature comes on only after several
minutes, then progressively increases, and persists for many minutes--it
may be hours. The two phenomena