iv ELECTROMOTIVE ACTION IX MUSCLE 423 



section of the leg muscles of a strychninised frog. In favourable 

 cases, " the rheoscopic leg set up a series of weak twitches which, 

 though connected, were never very close together " ; it usually 

 remained quiescent. 



Friedrich (I.e. p. 422) made the same experiment on frogs, 

 rabbits, and guinea-pigs. Single twitches, which preceded the 

 spasm of tetanus proper, generally caused secondary twitches. 

 An even (strychnia) tetanus, on the contrary even if there was 

 not, as frequently, a total failure of action produced secondary 

 twitches at the commencement only, never secondary tetanus. 

 Effects, corresponding with those observed by du Bois-Keymond, 

 occur only when the primary preparation, instead of exhibiting a 

 steady tetanus, goes into clonic spasm. In other respects strychnia 

 tetanus has a marked action on the superposed nerve. Strong 

 secondary initial twitches accompany almost every spasm of 

 rigor in frogs that have been kept in very dilute solution of 

 strychnia, until for hours, and even days, they will exhibit 

 heightened reflexes ; the nerve need only be in contact with the 

 skin of the leg in the intact animal (Kiihne, I.e. p. 60). 



Sustained voluntary and reflex contraction is as little apt to 

 excite secondary tetanus as strychnia spasm. Harless was the 

 first who tried to obtain secondary action from the exposed 

 gastrocnemius of an otherwise intact frog, during its natural 

 movements. Even when sustained contraction had been induced 

 in the muscle by painful excitation, Harless failed to dis- 

 cover secondary tetanus ; there was at most a secondary twitch 

 at the beginning of the contraction. Exactly the same occurred 

 in the reflex movements. Another experiment of Harless' is in- 

 teresting, where (in the frog) first the spinal cord and then the 

 sciatic plexus, high up, were electrically excited. In the former 

 case a secondary initial twitch only appeared, in the latter there 

 was invariably secondary tetanus. In this connection we may 

 quote the observations of Hering on the contraction of the 

 diaphragm in tetanus, occurring in respiration ; it is not pos- 

 sible to obtain secondary tetanus of a frog's leg, with applied 

 nerve, from the contracted diaphragm, although the same pre- 

 paration falls into secondary tetanus directly the phrenic nerve is 

 tetanised by weak electrical excitation, and gives a tertiary 

 twitch if the nerve of the diaphragm is divided high up and laid 

 on the still beating heart, so that the diaphragm is brought into 



