Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

physical condition. It is plain, that excess of pressure may cause fatal coma, or defect of the usual pressure fatal syncope, and yet no evidence- of the operation of the cause be left in the dead brain. It is certain, then, that, whether the cerebral pulp yields or not, there is a constant alternation of a greater and then of a less, compressing force exerted upon it during life. It is not improbable that this continual variation of the compressing force may be essential to the performance of the cerebral func- tions. May not the brain be thus incessantly charged, says Dr. Watson, if indeed it be, as has been suggested by no less a phi- losopher than Sir John Herschell, " an electric pile constantly in action," discharging itself by the nerves at brief intervals, " when the tension of the nervo-electricity, developed, reaches a certain point" ? However this may be, it is equally certain that, at times, or under certain conditions, the compressing force on the brain may greatly transgress its natural range and limits in either direction, — i.e., it maybe too great or too little. The functions of the nervous centres are thus liable to be deviated, perverted, or lost, both when the pressure becomes excessive, or, on the other hand, when the brain pressure is insufficient. In speaking of Hypercesthesia, and the diagnosis of diseases of the nervous system, and more especially of the sensory nerves, Dr. T. Laycock says, " Pain is preeminently the symptom by which we become conscious of disease in the organism ; it is, in effect, the sentinel that warns us of impending danger." By the term hyperesthesia, this condition of the nerves is meant, viz., an exalted susceptibility to impressions; a condi- tion expressed by tenderness;—pain and tenderness are its characteristics. Not in virtue of a change in the tissues that surround the nerve fibrils, and thus involving them as in inflam- mation ; biit in virtue of a change that is limited to the nerves, in some part of their route from centre to periphery. The pain that arises from a morbid state of the nerves only, and the pain that arises from a morbid condition of the tissues, to which those nerves minister, are, therefore, expressive of two widely 30