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UNCONSCIOUSNESS, a condition of little or no consciousness. The definition of con sciousness (q.v.) has been given in another vol ume and it remains here to consider those de grees and kinds of deviations from ordinary conscious states, particularly in the subnormal depressions. Under unconsciousness may be grouped two or three types. There may be total abeyance, such as is seen in epilepsy, in sleep, in brain concussion, in severe injuries, in infectious diseases, in drugs, as anaesthetics, hypnotics, alcohols, etc. There may be sub normal conditions, semi-conscious, subconscious states which would properly be classed here, for in certain conditions, such as in some epileptics, some alcoholics or hysterics, consciousness at one time may be acute and yet all memory of the former state may be obliterated in another condition. Some of these conditions are grouped under the heading of double personali ties. Some of these represent true phenomena, the vast majority are frauds. Thus from the minor forms of eabsent-mindednessn through sleep, up to the deepest grades of unconscious ness produced by drugs, one can observe in life all the many steps of a large variety of uncoil. serous phenomena. The site of consciousness has already been discussed and its coexistence with the entire nervous system maintained, but clinically it appears under many exciting causes.

The most important of these are: Unconsciousness due to 1. Convulsions of unknown origin.

2. Epilepsy.

3. Hysteria.

4. Organic brain diseases.

5. Organic heart diseases.

6. Toxic causes.— poisonings, endogenous and exogenous.

7. Traumatism.

(1) In childhood convulsions with uncon sciousness come on from a large number of unknown causes. Fear, anger, high temperature, teething, worms, are some of the actual irri tants in many of these instances; but in many no cause, immediate or remote, is to be found. Many of these attacks resemble attacks of epilepsy. They are to be carefully watched to determine this point, otherwise much harm may come, particularly if they are mild epileptic attacks and the epileptic habit be engendered by carelessness in treatment. Sometimes these con vulsions leave permanent brain injuries, but the majority recover without serious after effects. Convulsions in a child of unknown origin should mean to the mother that the nervous system is very readily upset and special precaution should be taken to avoid all forms of excitement in such children.

(2) Epilepsy. The most common form of unconsciousness in epilepsy has already been discussed (see EPILEPSY), but there are in some epileptics minor alterations of conscious ness that are of much importance. In some

epileptics the patient, while not truly unconscious, yet may be so engrossed in a dominating idea that all outside elements of attention are ex cluded. Thus some of this class may rob, murder, burn, roam off for days or even weeks, and yet on their return to their so-called normal conscious state, they may be absolutely oblivious to all that has happened. Such states are not uncommon in epileptics, but they are very rare outside of this condition and hysteria.

(3) Hysteria (q.v.). In this disease uncon sciousness is rarely complete. Consciousness is altered. These changes are fully discussed. Also see INSANITY ; PARANOIA.

(4) Organic Brain Disease. A number of brain diseases may cause unconsciousness. The most common are meningitis, hemorrhage, thrombosis, embolism, tumors, organic de. mentias. Under the general term apoplexy is included three separate disorders, all of which have similar symptoms. These are hemorrhage, embolism, thrombosis. In the a blood vessel in the brain breaks and there is destruc tion of brain tissue, in the second, a clot, usually from a larger blood vessel, is swept into a smaller blood vessel of the brain, cutting off the blood supply of a part of the brain. In a third a disease of the wall of the blood vessel causes a local clot which fills up the vessel and in the same manner deprives a part of the brain of blood. In all of these conditions a estroke,s or apoplexy, with unconsciousness occurs. The individual symptoms may be consulted under apoplexy, hemorrhage of brain, embolism, etc. In general paralysis of the insane, attacks of unconsciousness are a regular part of the de f velo ment of the disease. See GENERAL PARESIS.

(5) Some forms of heart disease are at ten ed with fainting attacks. In these the valves of the heart are found to act in a fective manner. See HEART, DISEASE OF THE.

(6) For a consideration of the toxic causes of unconsciousness see article on TOXICOLOGY.

(7) Traumatism, such as blows on the head, severe falls, sunstroke, all give rise to uncon sciousness. The two former conditions have been discussed under concussion — the last under sunstroke. See CONSCIOUSNESS ; CON SCIOUSNESS, DISORDERS OF; CONSCIOUSNESS, BIO LOGICAL ASPECTS OF, and consult bibliography under the first of these.