384 SEA-SIDE STUDIES. 



to mention the fact of so many animals being without fibres 

 at all * 



From what has been already said, the conclusion is inevit- 

 able that the conduction of nerve force does not take place 

 by means of fibres only. The fibres may by special organs 

 of conduction, and as special organs, a corresponding specialty 

 of function must be assigned to them ; and into this we must 

 now inquire. 



Let us assume that the homogeneous nerve transmits the 

 impression in a mass, just as the sounding-board of a piano, 

 if struck, will yield a certain resonance ; but the fibrous 

 nerve will transmit the impression along each separate fibre, 

 like the sounding-board when struck by keys ; the amount of 

 nervous impression and the amount of sound in each case 

 may be equal, but the varieties and combinations possible to 

 the latter are impossible to the former. Or to vary the illus- 

 tration, let us assume two men to be equally susceptible to 

 the general efiect of colour, but one of them, an artist, to 

 have more susceptibility to the minute difierences of colour ; 

 although the neivous impression may be equal in the two, it 

 will ])e less homogeneous in the artist, whom we may suppose 

 to have a more specialised retina. 



The assumption that fibres are organs of conduction at all, 

 may be disputed ; nor, if what was previously said respect- 



* Meissner's observations furnish a verj' noticeable fact, namely, that while 

 in Mermis Albicans the trunks are homogeneous, in another species, Mermis 

 nigre-^cens, they are fibrous ! In the face of such evidence no single exception 

 to the facts I have stated would surprise me — for instance, that fibres could be 

 found in a Doris, a Pfeurohranchiis, an Aplj/sia, or a iSolen — such exceptions 

 would in nowise invalidate my conclusions, for which, indeed, one single case 

 of non-fibiillated nerve would bo ample evidence. 



