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The most probable opinion would seem to be that found in Maimonides and many later writers, according to which the Hebrew 'ezob is to be identified with the Arabic sa'atar, now understood to be Satureja Thymus, a plant of very frequent occurrence in Syria and Palestine. with which Thymus Serpyllum, or wild thyme, and Satureja Thymbra are closely allied. Its smell, taste and medicinal properties are similar to those of H. officinalis. In Morocco the sa'atar of the Arabs is Origanum compactum; and it appears probable that several plants of the genera Thymus, Origanum and others nearly allied in form and habit, and found in similar localities, were used under the name of hyssop.

HYSTASPES (the Greek form of the Persian Vishtāspa). (1) A semi-legendary king (kava), praised by Zoroaster as his protector and a true believer, son of Aurvataspa (Lohrasp). The later tradition and the Shahname of Firdousi makes him (in the modern form Kai Gushtāsp) king of Iran. As Zoroaster probably preached his religion in eastern Iran, Vishtāspa must have been a dynast in Bactria or Sogdiana. The Zoroastrian religion was already dominant in Media in the time of the Assyrian king Sargon (c. 715 B.C.), and had been propagated here probably in much earlier times (cf. Persia); the time of Zoroaster and Vishtaspa may therefore be put at c. 1000 B.C. (2) A Persian, father of Darius I., under whose reign he was governor of Parthia, as Darius himself mentions in the Behistun inscription (2. 65). By Ammianus Marcellinus, xxiii. 6. 32, and by many modern authors he has been identified with the protector of Zoroaster, which is equally impossible for chronological and historical reasons, and'from the evidence of the development of Zoroastrianism itself (see Persia: Ancient History).  (Ed. M.) 

HYSTERESIS (Gr. ὑστέρησις, from ὑστέρειν, to lag behind), a term added to the vocabulary of physical science by J. A. Ewing, who defines it as follows: When there are two qualities M and N such that cyclic variations of N cause cyclic variations of M, then if the changes of M lag behind those of N, we may say that there is hysteresis in the relation of M to N (Phil. Trans., 1885, 176, p. 524). The phenomenon is best known in connexion with magnetism. If an iron bar is subjected to a magnetic force which is first gradually increased to a maximum and then gradually diminished, the resulting magnetization of the bar for any given value of the magnetic force will be greater when the force is decreasing than when it is increasing; the iron always tends to retain the magnetic condition which it has previously acquired, and changes of its magnetization consequently lag behind changes of the magnetic force. Thus there is hysteresis in the relation of magnetization to magnetic force. In consequence of hysteresis the process of magnetizing a piece of iron to a certain intensity and then restoring it to its original condition, or of effecting a double reversal of its magnetization, involves the expenditure of energy, which is dissipated as heat in the iron. Electrical generators and transformers often contain pieces of iron the magnetization of which is reversed many times in a second, and in order to economize power and to avoid undue heating it is essential that hysteresis should in such cases be as small as possible. Iron and mild steels showing remarkably little hysteresis are now specially manufactured for use in the construction of electrical machinery. (See Magnetism.)

HYSTERIA, a term applied to an affection which may manifest itself by a variety of symptoms, and which depends upon a disordered condition of the highest nervous centres. It is characterized by psychical peculiarities, while in addition there is often derangement of the functions sub served by the lower cerebral and spinal centres. Histological examination of the nervous system has failed to disclose associated structural alterations.

By the ancients and by modern physicians down to the time of Sydenham the symptoms of hysteria were supposed to be directly due to disturbances of the uterus (Gr. ὑστέρα, whence the name). This view is now universally recognized to be erroneous. The term “ functional ” is often used by English neurologists as synonymous with hysterical, a nomenclature which is tentatively advantageous since it is at least non-committal. P. J. Möbius has defined hysteria as “ a state in which ideas control the body and produce morbid changes in its functions.” P. Janet, who has done much to popularize the psychical origin of the affection, holds that there is “ a limitation of the field of consciousness ” comparable to the contraction of the visual fields met with in the disease. The hysterical subject, according to this view, is incapable of taking into the field of consciousness all the impressions of which the normal individual is conscious. Strong momentary impressions are no longer controlled so efficiently because of the defective simultaneous impressions of previous memories. Hence the readiness with which the impulse of the moment is obeyed, the loss of emotional control and the increased susceptibility to external suggestion, which are so characteristic. A secondary subconscious mental state is engendered by the relegation of less prominent impressions to a lower sphere: The dual personality which is typically exemplified in somnambulism and in the hypnotic state is thus induced. The explanation of hysterical symptoms which are independent of the will, and of the existence of which the individual may be unaware, is to be found in a relative preponderance of this secondary subconscious state as compared with the primary conscious personality. An elaboration of this theory affords an explanation of hysterical symptoms dependent upon a “ fixed idea.” The following definition of hysteria has recently been advanced by J. F. F. Babinski: “ Hysteria is a psychical condition manifesting itself principally by signs that may be termed primary, and in an accessory sense others that we may call secondary. The characteristic of the primary signs is that they may be exactly reproduced in certain subjects by suggestion and dispelled by persuasion. The characteristic of the secondary signs is that they are closely related to the primary phenomena.”

The causes of hysteria. may be divided into (a) the predisposing, such as hereditary predisposition to nervous disease, sex, age and national idiosyncrasy; and (b) the immediate, such as mental and physical exhaustion, fright and other emotional influences, pregnancy, the puerperal condition, diseases of the uterus and its appendages, and the depressing influence of injury or general disease. Perhaps, taken over all, hereditary predisposition to nerve-instability may be asserted as the most prolific cause. There is frequently direct inheritance, and cases of epilepsy and insanity or other form of nervous disease are rarely wanting when the family history is carefully enquired into. As regards age, the condition is appear at the evolution periods of life—puberty, pregnancy and the climacteric—without any further assignable cause except that first spoken of. It is rare in young children, but very frequent in girls between the ages of fifteen and twenty-five, while it sometimes manifests itself in women at the menopause. It is much more common in the female than in the male—in the proportion of 20 to 1. Certain races are more liable to the disease than others; thus the Latin races are much more prone to hysteria than are those who come of a Teutonic stock, and in more aggravated and complex forms. In England it has been asserted that an undue proportion of cases occur among Jews. Occupation, or be it rather said want of occupation, Is a prolific cause. This is noticeable more especially in the higher classes of society. An hysterical attack may occur as an immediate sequel to an epileptic fit. If the patient suffers only from petit mal (see Epilepsy), unaccompanied by true epileptic fits, the significance of the hysterical seizure, which is really a post-epileptic phenomenon, may remain unrecognized.

It is convenient to group the very varied symptoms of hysteria into paroxysmal and chronic. The popular term “ hysterics ” is applied to an explosion of emotionalism, generally the result of mental excitement, on which convulsive fits may supervene. The characters of these vary, and may closely resemble epilepsy. The hysterical fit is generally preceded by an aura or warning. This sometimes takes the form of a sensation as of a lump in the throat (globus hystericus). The patient may fall, but very rarely is injured in so doing. The eyes are often tightly closed, the body and limbs become rigid, and the back may become so arched that the patient rests on her heels and head (opisthotonos). This stage is usually followed by violent struggling movements. There

is no loss of consciousness. The attack may last for half-an-hour