76 PHYSIOLOGY OF LIFE. 



malcula infusoria became, by a vital oxydation, granular 

 in the polypi. This granulation formed itself into distinct 

 organs in the molluscs ; while for the snails, which are the 

 next step, the animalized lime, that seemed the sole final 

 cause of the life of the polypi, assumes all the characters of 

 an ulterior purpose. Refined into a horn-like substance, it 

 becomes to the snails the substitute of an organ, and their 

 outward skeleton. Yet how much more manifold and 

 definite, the organization of an insect, than that of the 

 preceding class, the patient researches of Swammerdam 

 and Lyonnet have evinced, to the delight and admiration 

 of every reflecting mind. 



In the insect, for the first time, we find the distinct 

 commencement of a separation between the exponents of 

 sensibility and those of irritability ; i. e. between the 

 nervous and the muscular system. The latter, however, 

 asserts its pre-eminence throughout. The prodigal pro- 

 vision of organs for the purposes of respiration, and the 

 marvellous powers which numerous tribes of insects pos- 

 sess, of accommodating the most corrupted airs, for a 

 longer or shorter period, to the support of their excitability, 

 would of itself lead us to presume, that here the vis 

 irritabilis is the reigning dynasty. There is here no con- 

 fluence of nerves into one reservoir, as evidence of the 

 independent existence of sensibility as sensibility; and 

 therefore no counterpoise of a vascular system, as a distinct 

 exponent of the irritable pole. The whole muscularity of 

 these animals, is the organ of irritability ; and the nerves 

 themselves are probably feeders of the motory power. 

 The petty rills of sensibility flow into the full expanse of 

 irritability, and there lose themselves. The nerves apper- 



