being thus differently developed, it is
impossible that they should have the relation of cause and effect, and
the fall of temperature must be traced to a direct influence of the
nervous system upon the chemical processes of the body.

This lowering of temperature under the influence of a powerful
irritation of a nerve-trunk or of its minute branches, which everywhere
pervade the tissues and spread out in the skin, is common to all species
of mammals. If a rabbit be merely tied down tightly upon a table, the
fall is perceptible, and if it be severely wounded, the temperature
diminishes very greatly. It has long been known that severe burns are
followed by a very great depression of the animal heat. Redard, a French
physician, made during the late siege of Paris a most interesting series
of observations upon the influence of severe gunshot wounds. He found
that, entirely independent of any haemorrhage which might have occurred,
the temperature fell enormously, and in direct proportion to the gravity
of the wound; so that by the aid of the thermometer he was able to
predict whether a fatal issue would or would not occur in the course of
a few hours.

We have found that both in man and the lower animals the nervous system
is able to check the chemical movements of the body, but before we can
decide how it does so facts not yet noticed must be looked at.

If the spinal cord of an animal be cut just below the origin of the
nerves of respiration, an immediate fall of temperature occurs, and, if
the animal be left in a cool room, persists until death ensues. If,
however, the victim be put in a warm place, after a time the temperature
begins to rise, and finally a most intense fever is developed. Parallel
phenomena follow division of the spinal cord in man. Indeed, Sir
Benjamin Brodie was first led to experiment upon animals by observing in
1837 an excessive fever follow in a patient a wound of the spinal cord.

I have already explained, in a former number of this Magazine,[2] the
nature of the so-called vaso-motor nerves, which preside over the little
circular muscles that run round and round in the coats of the
blood-vessels. When they are excited, these muscles contract and the
size of the arteries is diminished: when they are paralyzed, the
arterial inner muscles relax and the vessels dilate. The vaso-motor
nerves have their governing centre in that upper portion of the spinal
cord which is within the skull, the so-calle