436 



Dr. W. Kulme. On the 



nerve is divided and artificially excited at the peripheral end, the 

 muscles betray it. On the other hand, no visible physiological reac- 

 tion is found at the central origin of the motor fibre when stimulated 

 at the periphery, so that at first we were quite in darkness as to 

 whether in general it conducted ceatripetally. Nature, however, 

 has presented us with a contrivance by which we are enabled to 

 demonstrate the possibility of such an inverted or centripetal nerve- 

 conduction. The contrivance consists in the branching division of 

 nerve-fibres so frequently found in muscles, as will at once be seen in 

 a preparation from a frog (fig. 3). In many muscles these branchings 

 are so arranged that we can use them for an experiment as simple as 

 it is conclusive of nerve- conduction in both directions. 



Fig. 3. Fig. 4. 



In the gracilis muscle of the frog the nervation is fashioned in the 

 manner displayed schematically upon this diagram (fig. 4) and in more 

 detail on the following (fig. 5). In reality the arrangement is like this. 

 Now, if I cut up the muscle according to this diagram (fig. 6), we get 

 at the tip Z nerve-fibres which are connected with the muscle-fibres at 

 O and U only by the branchings at the points xx, but which in life 

 served only for the parts of the muscle removed at / and/'. 



An experiment (13), viz., the stimulation of z (fig. 6), will now 

 convince you that nerves severed from their own muscle-fibres act 

 quite well backwards upon those placed centripetal to them, which they 

 can only do if nerves can also conduct centripetally, and so long as a 

 path is preserved for this through the branchings. If we cut out the 

 neighbourhood of the branchings it is all over with the reaction of the 

 muscle. 



We can make another experiment on the same muscle (14). We 

 see that when we excite the lower tip of the muscle, only the lower 

 portion twitches and not the upper. The two portions are in fact 



