242 LOCALIZED ELECTRIZATION. 



Tlie graduation should be made upon a scale sufficiently extensive 

 to measure every degree of intensity of the current, in proportion to 

 the degree of excitability of every organ. 



It is, therefore, necessary that a faradic apparatus should admit 

 of being rendered very powerful or very feeble, according to the 

 indications to be fulfilled, and by the aid of an independent system 

 of graduation, calculated exactly to measure and to distribute 

 either powerful or feeble currents. 



Lastly, it is necessary, in a volta-electric apparatus, that the 

 initial force of the battery should always act with the same degree 

 of intensity, or, at least, that its intensity should be known to the 

 operator. But the battery which works a volta-faradic apparatus 

 will be more or less constant, accordingly as its acids are more or 

 less concentrated, accordingly as it polarises or exhausts itself 

 more or less quickly, or accordingly as it becomes more or less 

 choked by imperfectly conducting crystallized salts. We may see 

 that, with such variations in the initial force, the measurement of 

 the electric doses becomes illusory, and that hence it is impossible 

 exactly to formulate the doses of electricity wliich may properly 

 be administered to every organ. 



Such are the principal properties which should be found united 

 in every faradic apparatus intended for electro-physiological or 

 pathological study, or for therapeutical employment. There are 

 yet others which it is very important to obtain. Thus, the instru- 

 ments should be portable, easy of management, and moderate in 

 price. But, as these conditions involve no scientific question, I 

 have not thought it desirable to discuss them in this place, and 

 shall return to them hereafter. Although secondary, they have 

 very great bearing upon the practice of medical electricity. 



In the first edition I added to the account of the different proper- 

 ties of the several currents of the induction apparatus, a critical 

 examination of the instruments then in use in medical practice ; 

 and showed that they did not combine the whole of tlie conditions 

 necessary for localized faradization, or for the application of this 

 kind of electricity to my electro-physiological researches ; and 

 that they did not fulfil the requirements of electro-therapeutics. 



This critical examination has borne its fruits. In fact, the 

 utility of the employment of localized faradization in the study 

 of muscular pliysiology and pathology, and the general diffusion of 

 electric treatment, have produced great activity in the commercial 

 manufacture of induction instruments. Hence it has followed, that 

 physicists and manufacturers — the former to aid in the growth of 

 knowledge, the latter to obtain the patronage of physicians — have 

 alike striven to improve the instruments and to bring them to 



