The nerves which form the very complicated system of gelatinous cords of
various sizes which emanate from the brain and the spinal cord, send
thousands of branches throughout the entire body. They communicate the
impressions from the outside to the brain and convey its conscious or
unconscious (instinctive) mandate to the muscles of all organs.
The nerves are fed by the lymphatic system and are everywhere
accompanied by blood-vessles, and the oxygenous blood in the latter
conveys the oxygen to the nerve substance, which it consumes and thus
develops power sufficient to execute the various functions.
Naturally the supply that replaces the burned nerve substance, must be
adequate, and if for any reason whatsoever more nerve substance is
consumed than the body is able to renew by the time it is needed, the
nerve system becomes degenerated and numerous disturbances are the
consequence.
This is the great field of mental functions and disturbances, of moods
and reactions on muscular tracts which in themselves are healthy, but
are paralyzed in their work through the defective functioning of the
power-conveying nerves.
Again it is impossible here to give more than a general description,
showing on what conditions nervous diseases are based. The manifold
manifestations of this degeneration were combined into groups under the
old system in which the Greek name of a system was everything, its
practical explanation but little.
The principal ways in which these degenerations manifest themselves are
pains, mental agony and derangement, temporary cessation of functions,
cramps, involuntary movements and similar disturbances.
The names generally applied to them are neuralgia and neuritis,--causing
pains in the nerves of certain parts of the body; neurasthenia,--consisting
mainly of the complete relaxation of tension in the nervous system, causing
sadness, inability for work, etc.; asthma, cramp-like cessation of certain
functions of the small vessels of the lungs, alveoli, which impedes
respiration; epilepsy, temporary cramp in the greater part of the body,
causing loss of consciousness, involuntary movements of the limbs, etc.;
St. Vitus's dance,--a similar affection, usually in children.
While the complicated nature of nerve diseases requires very careful
treatment of great individual variety, the general rule is that the
re-enforcement of the nerves with the material of which they are built,
together with regeneration of the blood, which, when in normal condition
prevents such disturbances, will bring about a cure. Of course this is
sometimes a slow process, especially when, as in the case of epilepsy,
the nervous disease is of an hereditary character, and the resistant
power of the nerves is correspondingly weak.
In regard to one of the most disastrous diseases, caused by degeneration
of the most important nerve i.e. the Vagus, see under "Catarrh"--section
VI.