ORIGIN OF NERVES. 385 



ganglion-c'ell and the muscle-cell to be so rapid as to render it 

 impossible for the growth of the connecting nerve to keep pace 

 with it, and that thus the process connecting the ganglion-cell 

 and the muscle-cell might become ruptured. Nevertheless the 

 tendency of the process to grow from the ganglion-cell to the 

 muscle-cell, would remain, and when the rapid developmental 

 growth had ceased, the two would become united again by the 

 growth of the process which had previously been ruptured. It 

 will be seen that this hypothesis, which I have considered only 

 with reference to a single nerve and muscle-cell, might be 

 extended so as to apply to a complicated central nervous system 

 and peripheral nerves and muscles, and also could apply equally 

 as well to the sensory as to the motor terminations of a nerve. 

 In the case of the sensory termination, we should only have to 

 suppose that the centre nervous cell became more and more 

 separated by the general growth from the recipient terminal 

 sensory cell, and that during the general growth the connection 

 between the two was mechanically ruptured but restored again 

 on the termination of the more rapid growth. 



As the descendants of the animal in which the rupture 

 occurred became progressively more complicated, the two ter- 

 minal cells must have become widely separated at a continually 

 earlier period, till finally they may have been separated at a 

 period of development when they were indistinguishable from 

 the surrounding embryonic cells ; and since the rupture would 

 also occur at this period, the primitive junction between the 

 nerve-centre and termination would escape detection. The object 

 of this hypothesis is to explain the facts, so far as they are known, 

 of the development of the nervous system in Vertebrates. 



In Vertebrates we certainly appear to have an outgrowth 

 from the nervous system, which eventually becomes united 

 with the muscle or sensory terminal organs. The ingenious 

 hypothetical scheme of development of the nerves given by 

 Hensen 1 would be far preferable to the one suggested if it could 

 be brought into conformity with the facts. There is, however, 

 at present no evidence for Hensen's view, as he himself admits, 

 but considering how little we know of the finer details of the 

 development of nerves, it seems not impossible that such 



1 Virchow's Archiv, Vol. xxxi. 1864. 



