366 MESSRS. F. GOTCH AND V. HORSLEY 



Similar attempts have been made to determine the rate of conduction of nerve 

 impulses in the spinal cord, both centrifugal a,nd centripetal in character. Most of 

 the experiments have been made upon Man by measuring the reaction time, and are 

 therefore more or less untrustworthy owing to the conditions just mentioned. EXNER* 

 obtained thus a mean result for centrifugal impulses of 11 to 12 metres in 1 second, 

 for centripetal impulses of 8 metres. On the other hand, VON WiTTiCH,t by the use 

 of a similar method, had previously obtained a rate of 26 metres for the centrifugal 

 impulses. We have been unable to find any description of observations upon the Cat 

 with regard to conduction, though such might easily be carried out by the use of the 

 graphic method, and since it was important for us to know the behaviour of the 

 fibres in the cord in this respect, we devoted a few preliminary experiments to the 

 determination of conduction time only. 



These experiments may be briefly described as follows : - 



The cord was exposed in the anresthetised animal in the lower cervical and lower 

 dorsal regions respectively ; the rectus femoris muscle was then selected for graphic 

 record. The advantages offered by this muscle are 



(1.) Its anatomical relation with the pelvis, enabling the leg and trunk to be fixed, 



and the muscle brought out at right angles to the body. 

 (2.) The ease with which it could be separated from the surrounding parts. 

 (3.) Its own structure that of a long thin muscle, with parallel fibres. 



The lower tendon of the muscle was divided and ligatured ; the ligature was then 

 attached by means of a pulley to the lever of TIGERSTEDT'S break key 4: so adjusted 

 that the smallest contraction of the muscle was sufficient to raise the lever, and thus 

 break an electrical contact. This contact formed part of an independent circuit, 

 including one of SMITH'S new chronographs and three storage cells ; it was ascertained 

 that the movements of the chronograph armature occurred within 3/10000 second of 

 the break of the circuit. 



The movement of the chronograph lever recorded upon the travelling glass plate of a 

 spring myograph (Federmyographion), the rate of movement being 25 centims. in 

 1/100 sec. The lateral column of the exposed cord was excited by a single 

 induction shock, which was obtained by allowing the traveller to break, at a given 

 point of its course, the primary circuit of a KBONECKER'S inductorium. As the 

 moment of break was always the same, the break induction shock obtained was 

 uniform in all cases, both as to intensity and time of occurrence ; the position of the 

 secondary coil was 2000. 



The following measurements were obtained of the duration of the period between 



* EXNEE, PFLUGEK'S ' Archiv, 1 1873, vol. 7, p. 632. 



t v. WITTICH, ' Archiv f. Pathol. Anat.,' 1869, vol. 46, p. 476. 



t Loc. tit. 



Loc. cit. 



