control the function of these organs, but partially by virtue of their inaccessibility, the real action of the sympathetic nervous system is not entirely known. It is controlled more definitely by thoughts and emotions than is the cerebro spinal system, and it is through the sympathetic nerve effect upon heart and vital organs that the thoughts materially affect the breath.

According to Langley, the efferent fibres from the sympathetic nerve cells supply the organs of the involuntary processes of the body,-those which maintain life without volition; as it was termed in olden times-the vegetative processes of the body. Langley terms these efferent fibres controlling the vegetative processes, autonomic nerves.

While the sympathetic nerves have their rise in the central nervous system, they possess a certain independence of it. The spinal nerves are, however, connected with many of the sympathetic ganglia. Figure 12 illustrates diagrammatically the manner of connection between the central nervous system and the sympathetic nerves.

By reference to Figure 12, it will be noted how very closely connected are the solar plexus nerves controlling the stomach with the hypogastric nerves to the pelvis and abdomen.

It will be readily seen by this how disturbance in the abdomen so quickly disturbs the stomach. The large sympathetic ganglion, known as the solar plexus, is clearly shown on this figure. It lies posterior to the stomach, and in front of the spinal cord. This ganglion is so important in the control of vital life that ancients located the soul here:

With the exception of the ciliary muscle of the eye, which is partially under voluntary control, practically all of the sympathetic nerve fibres are removed from the control of the will.

Some of the sympathetic nerve fibres are white and others gray, appearing to consist of an axis cylinder without surrounding myelin.

The sympathetic nerves convey both sensory and motor impulses, but they act, as has been illustrated in case of adjust

ment of the lens of the eye, more slowly than do the cerebro spinal nerves.

If the extremity of a sympathetic nerve be irritated by an injury or by pressure, because of inflammation or congestion of the vital organs, the reflex motion is slow. The slowness of this action is illustrated by the condition termed a "cold," which may not localize in a given organ under fifteen to twenty-four hours after the exposure causing the condition.*

It is hard to make one who has not had actual experience, realize how quickly the relief from a cold is established by vigorous exercise. The patient, as a rule, feels weak and disinclined to movement, but it is here that will power and strength of character show mental control of bodily functioning.

*Publishers' Note:-For the physiological description of a cold, see Miss Cocroft's book upon Foods.

NERVE IMPULSE

The nature of the nerve impulse and the manner of its conveyance has always been of deepest interest to physiologists. For many years it was believed that the nerves were tubes through which flowed an exceedingly fine matter in gaseous form, known as "animal spirits." Again it was supposed to be a fluid and called "nerve juice."

At one time this nerve impulse was supposed to be identical with electricity, but more recent experiments have proven this theory to be false, as is illustrated by the fact that if a nerve be tightly bound, the transmission of the impulse is interfered with, but the electrical current passes through the constricted nerve without interference. When a nerve receives a sensory or motor stimulation, so that an im