INTERNAL ANATOMY OF INSECTS. 3 



the CREATOR. Its pulpy substance is the visible medium 

 by which the governing principle a transmits its com- 

 mands to the various organs of the body, and they move 

 instantaneously yet this appears to be but the conduc- 

 tor of some higher principle, which can be more imme- 

 diately acted upon by the mind and by the will. This 

 principle, however, whatever it be, whether we call it the 

 nervous Jluid, or the nervous power b , has not been de- 

 tected, and is known only by its effects. The system of 

 which we are speaking may therefore be deemed the 

 foundation and root of the animal, the centre from which 

 emanate all its powers and functions. 



Comparative anatomists have considered the nervous 

 system of animals as formed upon four primary types, 

 which may be called the molecular, the filamentous^ the 

 ganglionic, and cerebro-spinal c . The Jirst is where in- 

 visible nervous molecules are dispersed in a gelatinous 

 body, the existence of which has only been ascertained 

 by the nervous irritability of such bodies, their fine sense 

 of touch, their perceiving the movements of the waters 

 in which they reside, and from their perfect sense of the 

 degrees of light and heat d . Of this description are the 

 infusory animals, and the Polypi. The nervous mole- 

 cules in these are conjectured to constitute so many gan- 

 glions, or centres of sensation and vitality e . The second, 

 the filamentous, is where the nervous system consists of 

 nervous threads radiating from the mouth, as in the 



3 To ' H-yeftouMov. 



b See Hooper's Medical Dictionary, under Nervous Fluid, and 

 Mr. Sandwith's useful Introduction to Anatomy and Physiology t 83. 



c N. Diet. d'Hist. Nat. xvi. 305. 



d Cuv. Anat. Comp. ii. 362. Compare MacLeay Hor. Entomolog. 

 215. e N. Diet. d'Hist. Nat. nbi. siipr. 



B2 



