58 ELECTRO-PHYSIOLOGY CHAP. 



is excited, and the excitation conducted in the first instance 

 centripetally. Later on, Kiihne attempted the same experi- 

 ment successfully on other muscles, e.g. in the frog's gracilis. 

 As is seen in Fig. 160 c, the entering nerve divides into two 

 branches a, b, one of which is cut round so as to form a lobe ; 

 and on exciting this (by incision) the whole muscle invariably 

 twitches. Since in this case also there are divisions of the fibres 

 at the point where the entire nerve divides, the experiment is 

 conclusive for centripetal conduction in the branch that supplies 

 the lobe. We shall return later on to Babuchin's experiment ; 

 in this there is a discharge of the entire organ when any twig of 

 the peripheral ramification of a single nerve-fibre is stimulated. 

 As in Kiihne's experiment, the excitation in the centrifugal nerves 

 must at first travel centripetally, in order to spread to all the 

 other branches (12). 



If the axis-cylinder were homogeneous, the bifurcate experi- 

 ment with sartorius, as well as the analogous experiments on 

 other muscles and on the electrical organ of Malapterurus, would 

 be clear and unimpeachable. On stimulating the lesser rami, the 

 excitation would take a backward course to the point of division, 

 and then presumably travel in the same centripetal direction along 

 the fibres of the trunk, taking the normal centrifugal path only in 

 the other peripheral ramifications. The axis- cylinder, however, is 

 not homogeneous, but is composed of fibrils, and there is much to 

 indicate that these are the true conducting elements. Hence we 

 cannot regard any tract of the nerve as a physiological unity, 

 but must recognise as many isolated paths of conduction as 

 there are fibrils. Then, however, the results of the bifurcate 

 experiment would, as Kiihne points out, be conclusive for double 

 conduction in the nerve under a succession of premises only. If 

 the law is admitted, it implies at the dividing point of a primitive 

 fibre a further division of axis - cylinder fibrils also (Kiihne). 

 When Max Schultze was elaborating Eemak's theory of the 

 fibrillar structure of the axis-cylinder he came to the opposite 

 conclusion. He believed the nerve-fibres to contain from the 

 outset all the fibrils destined for the peripheral expansions, so 

 that in the branching of the axis-cylinder there would only be 

 an unravelling, or bending aside, and no actual division of fibrils. 

 On the other hand, there are many facts against this conclusion. 

 Wherever nerve - division is present, the sum of the peripheral 



