should be taken only where the stomach is not eliminating sufficient gastric juices.

Normally all the digestive processes go on without our knowledge or consent. If however, some irritating substance, like a dose of castor oil, be taken, the sensory nerve fibres receive such a violent stimulus, that the message is not only carried to motor nerves through the motor cells, but is sent up through the posterior horn of the cord to the brain, because the motor nerve is acting so vigorously as to cause painful peristalsis.

Other reflex acts are the beating of the heart, breathing, coughing, sneezing, vomiting, the emptying of the bladder, parturition, etc. No brain impulse is needed for their performance.

A familiar example of reflex action, which demonstrates that this nerve force is sent from a nerve center rather than from the brain, is shown in the sudden jump or twitching of the muscles during sleep. It is not known what produces the sensation upon the nerve extremity; one theory is that the impression is made by

combustion of an undue amount of waste in any part of the system, due to sluggish circulation and to a failure of the system to regularly eliminate the waste during waking hours. Were one awake this nerve impulse would be inhibited, or restrained, by consciousness.

Nerve activity during sleep occurs most frequently when one is tired, because tired nerve cells do not properly instigate the removal of the normal amount of waste during waking hours; in nerve exhaustion, the breathing is not full, and the circulation is sluggish.

Another illustration of reflex action, which demonstrates also that nerve impulse originates in the nerve cells, and may be conducted without consciousness, is shown in the severance of the head of a chicken;the nerve sensation of the fall to the ground is conveyed to the spinal cord; a change takes place in the cell of the gray matter and a motor impulse is sent forth which causes the chicken to flutter and throw itself about, convulsive twitchings taking place from one to three minutes

after the head is severed. After the removal of the head of a frog, if the toe be pinched, the sensation is conveyed to the gray matter in the spinal cord and at once the leg is drawn up out of harm's way. On the other hand, if the spinal cord be destroyed, the nerves remaining intact, no such result follows, showing that the cord has the property of receiving sensations and sending out motor impulses, without dependence upon the brain.

If a child's foot be tickled during sleep, the foot will be drawn out of the way without his awakening, unless the annoyance be unduly persisted in, then a message is sent to the brain.

Familiar examples of reflex action, which illustrate the importance of this function in the preservation of bodily integrity are the instantaneous closing of an eyelid, when it would seem that some foreign article would strike the eyeball; the sudden recovery in falls or accidents; the involuntary step backward or forward removing the body out of harm's way, when a vehicle or a street car suddenly impedes the

progress. One is not conscious of the danger, as a rule, until after the reflex movement has taken place, thus showing that this reflex action is involuntary; yet it becomes a conscious matter after the mind has had time to act upon it.

When it is considered that all of the digestive and metabolic activities are controlled by this reflex action, that the nutriment is assimilated, etc., and the waste of the system is removed, and that the mind is left free for the instigation of comparatively few movements, it will be realized how the freedom, strength and nourishment of all nerves and the health and safety of the individual depend upon this reflex function.

A peculiar phenomenon, which Sensations Referred to puzzled scientists for many years, Extremities. lies in the fact that an injury to any portion of a nerve along its course is always referred to the extremity of that nerve, as is illustrated by the singular phenomenon that if a leg be amputated, the amputated part may be left hundreds of

miles away and yet any sensation upon the end of the nerve in the part of the leg remaining, will be conveyed to the nerve center and to the brain, the patient actually feeling the sensation as if the extremity, which has been removed, were still in place. If it were not for his sight, he would not believe that his leg was not still attached to his body, because the sensation is exactly the same as if it were there. This illustrates nerve habit.

Again,-if one compresses or receives a sudden blow upon the nerve back of the elbow, the sensation is referred to the little finger, to the ring finger, and to the outer side of the hand, up to the wrist. The sensation is so keen in the fingers that it seems as if the injury were done there. Pressure upon this ulnar nerve interferes with the flow of nourishment to the extremities of the nerve.

A similar sensation is felt when by reason of the position of the limbs, the nerve of the leg, which supplies the foot, is compressed;-a tingling sensation is felt in