iv GENERAL PHYSIOLOGY OF NERVOUS SYSTEM 199 



skin of the back, and dividing it when healed close to the root. 

 As he elicited signs of pain on exciting this inverted tail, he 

 concluded that conduction in the nerve had been reversed. But 

 till we know what phenomena of degeneration and regeneration 

 take place in the nerve, after transplanting the tail, it is impossible 

 to give any positive explanation of the results of this experiment, 

 and it cannot be invoked in favour of the law of double conduction. 



Kiihne (1859) attempted by another method to prove con- 

 duction in both directions. He divided the broad end of a freshly 

 dissected frog's sartorius into two strips with scissors, and found 

 that mechanical stimulation of one of the strips produced fibrillary 

 contractions which were not confined to the segment of muscle 

 that was directly excited, but spread also to the strip that had 

 not been excited. According to Kiihne this phenomenon can only 

 be explained on the assumption that the excited and non-excited 

 segments of muscle contain nerve- fibres which come from the 

 bifurcation of the axis-cylinders of the principal nerve. The 

 excitation is transmitted centripetally in the nerves of the first 

 strip, and then spreads centrifugally to the nerves of the second 

 strip. 



Babuchin repeated this experiment on the electrical organ of 

 Malapterurus which has a single gigantic many-branching nerve- 

 fibre. He found that excitation of a single twig of this fibre 

 suffices to produce a discharge of the whole electrical organ. 



Hermann attached great importance to these experiments of 

 Kiihne and Babuchin as evidence for the law of conduction in 

 both directions. Other authorities, on the contrary, make strong 

 objections, for which we have not space, particularly as Kiihne, 

 in a memoir of 1886, published a long series of new experiments 

 on the pectoral and gracilis muscles of the frog which lend them- 

 selves better to the solution of the problem. 



If the pectoral muscle of the frog is divided as shown in Fig. 

 130, by leaving a bridge (Z^ which carries the nerve and a few 

 muscle fibres, mechanical, chemical, or electrical stimulation of 

 this bit of tissue will cause the whole of the remainder of the 

 preparation (M) to contract. This contraction is not fibrillary as 

 in the sartorius, but diffuse and simultaneous in all the fibres of 

 the muscle, so that it can be graphically recorded and shown to 

 exhibit the characteristics of a single twitch. The experiment of 

 Fig. 131 is still more decisive. It shows that retrograde con- 

 duction of the nerve impulse along the motor fibres may also 

 occur between two parts of the same muscle (K and Z), united 

 only by the nerve (&), on stimulating one portion of the nerve (Z), 

 so that any direct intervention of the muscle fibres in causing 

 the phenomenon is excluded. 



Kiihne ascertained by a minute histological examination of 

 the nerves of the frog's pectoral and gracilis muscles that the 



