300 LECTURE XII. 



striking, as to incite the observer to reflection upon the 

 different qualities of these groups. 



In the course of time probably further distinctions. 

 perhaps even in the internal economy of these cells, 

 will be detected, but at present nothing more can be 

 stated concerning them. This is a very great and 

 lamentable void in our knowledge, and a void which 

 we now particularly feel, because this is just the place 

 where we should have to discuss the pacific action of 

 these different elements. But it must not be overlooked 

 that these conditions are among the most difficult which 

 are ever submitted to anatomical investigation, and that 

 one's endeavors to produce specimens of a character to 

 convince one's own eyes alone, nearly always fail, because 

 it is scarcely possible to succeed in effecting a real isola- 

 tion of the cells with all their processes and connections, 

 and because, on account of the extraordinary fragility of 

 these bodies, one is nearly always compelled to trace them 

 out in hardened sections. When sections are made of 

 structures which to a great extent are composed of fibres 

 and in which these run in a longitudinal, a transverse, or 

 an oblique direction, so that an interlacement is always 

 presented to the view, it depends of course entirely upon 

 a happy chance whether in a section the course of a sin- 

 gle fibre can be followed up over a large space with a 

 certain degree of distinctness. This difficulty can certainly 

 be lessened by making the sections in all possible direc- 

 tions and thus increasing the probability of at last stum- 

 bling upon the direction followed by the divisions of a 

 branch, but even then the obstacles still remain so great 

 that one can hardly expect, ever to be able to take in at 

 one view the whole of the ramifications and connections 

 of a cell belonging to the great nervous centres, that is 

 provided with at all a large number of branches. 



In this respect also the electrical organ of fishes has 



