DOUBLE-CUERENT MAGNETO-FAR ADIC APPARATUS. 269 



physiological and pathological experiments, and for treatment in 

 a few cases in which contractility or sensibility are either abolished 

 or sensibly diminished. 



The power of this small instrument is very considerable, regard 

 being had to the small size of its coil. This is not only due to 

 the excellent proportions of length and diameter of the wires, and 

 to good manufacture, but also and chiefly to the powerful mag- 

 netization of its band of soft iron rolled into a helix, which thus 

 offers a considerable extent of surface."* 



Part the Fourth. 

 the author's double-ouerent magneto-f arabic apparatus. 



The volta-faradic instruments, the construction and properties 

 of which have been described in the preceding Part, have been 

 employed in my numerous researches in electro-physiology, patho- 

 logy, and therapeutics. They have endured this test satisfactorily, 

 and their usefulness is now perfectly established. Unfortunately, 

 the preparation of the battery, simple though it be, necessarily 

 requires some amount of manipulation. This single inconvenience 

 has presented a difficulty to some physicians, and has often in- 

 duced them to prefer the common magneto-electric instrument. 



For this reason, I have endeavoured to give to a magneto- 

 electric instrument, as far as possible, the properties that I believe 

 to be indispensable for the practice of localized faradization. 



§ I. — DeSCRIPION of THE APPARATUS. 



My magneto-faradic apparatus (see fig. 64) is composed of a 

 magnet, of an armature, set in movement by a peculiar mechanism, 

 of a regulator of the armature, that is at once a moderator of the 

 currents and a magnetic tensor ; of two coils of copper wire, of 

 unequal length and thickness ; of a rheotome ; of a regulator 

 of the intermissions ; of a graduator of the currents ; and, lastly, of 

 a commutator of the coils. 



A. — The Magnet. 

 The magnet is formed of two parallel cylindrical branches, 



* I have experimented comparatively, 

 with different forms of core, with regard 

 to their respective physiological eflects; 

 using iron wires (after Dove's method), 



into a helix, and with its internal surface 

 insulated by a sheet of paper. I have 

 found that the helix of soft iron has given 

 the best results, both as regards the power 



split tubes of tin, enclosed the one within , of physiological effects and as regards 

 the other, and each insulated by a paper i the force of the magnetization, 

 covering, then a broad band of tin rolled | 



