390 SEA-SIDE STUDIES. 



special organ constantly before us. What would be 

 said of a man who called his gig a gondola, his steamer 

 a railway, his carriage a wheelbarrow ? The general 

 function of all these things is the same, but the sjjecial 

 office of each differs from that of the others, and its 

 structure bears reference to such sjDCcialty. In like 

 manner a "proboscis" is not a "hand," although both 

 are prehensile organs ; nor are contractile fibres " mus- 

 cles," although both subserve the same general func- 

 tion. 



Descending from these abstract considerations to the 

 particular subject now before us, namely, the nervous 

 system, we note first, that minute and laborious as the 

 researches have been, they have seldom taken the direc- 

 tion of comparative histology. The disposition of nerves 

 and ganglia, and the structure of particular parts, such 

 as the brain and spinal chord, have been studied with 

 splendid results ; but, as far as my reading extends, no 

 one has thouo-ht of makino; minute and extensive com- 

 parisons of the various specialties of nervous tissue ; 

 and the reason has been that men have assumed a nerve 

 to be always of one structure, forgetting Moliere's 

 humorous wisdom : il y a fagots et fagots. 



When I first examined the nervous system of the 

 Doris and Pleurohranchus, I was surprised to find the 

 brain (oesophageal ganglia) of an orange-red, and yel- 

 low colour, instead of white or grey. The fact is fami- 

 liar to anatomists, but the explanation given is more 

 than questionable. Von Siebold attributes it to pig- 

 ment scattered through the investing sheath (neuri- 



