150 ON NERVE-EXCITATION BY THE NERVE-CURRENT. 



In this experiment the secondary tetanus appears not merely in 

 the muscles which are innervated from the femoral branches of the 

 sciatic, but also in the muscles which are supplied by the crural 

 nerve, which arises from the plexus itself. If the femoral branch is 

 divided, and the sciatic isolated up to the origin of the crural, exci- 

 tation of the end of the sciatic at the knee gives rise to secondary 

 tetanus at the muscles innervated by the crural. I have also 

 isolated the sciatic nerve in its whole course down to the branch 

 which goes to the semimembranosus and rectus internus, then 

 divided the sciatic above the knee and removed all the rest of the 

 limb with the exception of the above-named muscles, and finally 

 separated the plexus from the spinal column, so that the whole 

 nerve, with these two muscles in connection with it, was completely 

 isolated. These muscles became secondarily tetanised when I 

 applied weak induction currents to the peripheral end of the 

 nerve. 



If instead of dividing the plexus I divided the spinal column 

 with its nerves between the seventh and eighth, or between the 

 eighth and ninth vertebrae, I only exceptionally obtained secondary 

 tetanus. But on the other hand, I have recorded one case in which 

 the division had been made between the sixth and seventh vertebrae, 

 and in which excitation of the peripheral end of the sciatic gave 

 rise to very strong secondary tetanus of the muscles of the thigh 

 and of the trunk on the corresponding side of the body. The mode 

 of this tetanus did not allow of its being considered as reflex, 

 although the incision had reached the lowest part of the spinal 

 cord which moreover, according to Engelhard 1 , is incapable of 

 giving reflex movements. 



If after division of the plexus I severed and excited one only 

 of the two branches into which the sciatic divides above the knee, 

 I obtained often, but not always, secondary effects which manifested 

 themselves, partly in the muscles of the thigh, partly in the leg 

 muscles supplied by the other of the two branches. But still 

 this secondary action rarely reached to a steady enduring tetanus, 

 and generally went no further than a tetanic agitation. Once 

 indeed I obtained secondary action by tetanising the sural nerve 

 which I had divided at the ankle joint and prepared up to the knee: 

 the toes spread out vigorously, and the gastrocnemius fell into 

 clonic contractions. Unfortunately the muscles of the thigh were 

 not observed, and I did not succeed in repeating the experiment 

 1 Muller's Arch. f. Anat. u. Physiol. Jahrg. 1841, p. 208. 



