134 



LIFE, IN ITS INTERMEDIATE FORMS. 



text of a lecture ; but still, if the function of the palate 

 have not utterly extinguished that of the eye, they can 

 scarcely have picked one of those dainty animals to pieces 

 without having observed that it is encased in a sort of 

 armour composed of many rings, the edges of which over- 

 lap, and which thus work one within the other. This 

 circumstance forms the most prominent characteristic of 

 a grand division of living beings, which are thence called 

 Annulosa (ringed), or Articulata (jointed). Another 

 mark of distinction is that their skeleton is external; the 

 outer skin, hardened in most cases into a horny crust, 

 affording attachment to the muscles, and giving by its 

 solidity and resistance precision and force to their con- 

 tractions. In some cases, indeed, this structure is less 

 obvious, the skin being rather membranous than crusta- 

 ceous, but even there it is more tough and leathery than 

 the internal parts. 



But the most important distinction of all, though it is 

 one which is appreciated only by the anatomist, is the 

 condition of the nervous system. That remarkable sub- 

 stance, murine — which is the material seat of all sensation, 

 and the proximate source of all motion, the ultimate link 

 of matter, whereby the spirit lays hold of it — is either 

 not discernible at all in the inferior creatures we have 

 been considering, or else exists only in the form of slen- 

 der threads, without any centres of accumulation. We 

 now no longer find it in this rudimentary condition. In 

 the Articulate animals there is a distinct arrangement of 

 the nerves, which, in general, run down the middle of the 

 body in two parallel cords, united at certain intervals by 

 knobs or aggregations of the nervous substance, called 



