ON THE MAMMALIAN NERVOUS SYSTEM. 91 



round it ; the two ends of the tie were then united together, thus forming a cable of 

 four strands. The end of this cable was fixed into a plug of kaolin moistened with 

 similar sodium chloride solution, which was united in the usual way with sulphate of 

 zinc kaolin paste, and this with the liquid in the one end of the U -tube. Since from 

 4 to 5 centims. of this yielding cable thus hung between the rigid part of the electrode 

 and the attached structure, this latter could be moved so as to isolate it from the 

 neighbouring tissues without interfering with its electrode connection, whilst, owing 

 to the soft cable being tied around the structure no displacement of the point of 

 contact was possible in consequence of such movement. 



2. The Exciting Arrangements. 



The method of excitation involved the use of (a) electrical, (6) mechanical, (c) 

 chemical stimuli. Of these the electrical, as alone admitting of accurate graduation, 

 is the most important. 



(a.) Electrical Excitation. The exciting arrangement involved in almost all cases the 

 production of a rapid succession of induction shocks. These were obtained from the 

 secondary coil of an induction apparatus of the general pattern of that devised 

 by DU BOIS-REYMOND, and usually employed in physiological research. The par- 

 ticular coil used was made and standardised in Berne, under Professor KRONECKER'S 

 direction, and differed from those ordinarily used in having a scale which denoted for 

 every position of the secondary coil, with reference to the primary, the relative 

 intensity of the current induction effect. (BowoiTCH.) Since the ordinary scale, 

 that of distance in centims. is most generally known to physiological workers, we 

 append the comparison of the numbers of the two systems showing their relative 

 intensity. 



Du Bois-Reymoiid inductorium scale. 



cm. 0. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.11.12.13.14.15.16.17.18.19.20.21.22.23.24.25 



Dl'vism-ntl n fOOOOOOOOOOOOOOOOOOOI>OCOCO'-J 

 ui v iftiuiis uj. (~) OO*O I s * *O O O O O O O O O O O <M O O TO CO QO r* O ^ ^ 



Kroiiecker in-' - "- . ^L 1 1 *- ^ w - w ''- w . ^ "*. ^ - ^ "* OT "*" rH "" 



CO<MOl.-HOO5COr-OO->JICO<Mi-Hi-Hrt 



ductormm. rH I-H I-H 1-1 I-H g 



scale. '-g g 







Two Daniell cells coupled for intensity were used in the circuit of the primary 

 induction coil ; this contained an automatic electro-magnetic vibrator, which closed 

 and opened the circuit 50 times per second. 



The interrupted circuit was a derivation bridging the primary coil (Helmholtz side- 

 wire), so that each interruption should induce make and break currents of approxi- 

 mately equal intensity, thus avoiding the accumulation of polarisation after-effects in 

 the excited tissue. The electrodes were well insulated platinum wires with points 

 1 millim, apart. When placed on the tip of the tongue, a slight acidity only was 



2 P 2 



