10 INTRODUCTORY CHAPTER. 



state of existence, as beautifully developed, and as care- 

 fully adapted to their necessities, as the highest instincts 

 of other classes are to their possessors. Nor is their 

 organization to be considered less perfect, because we 

 are unable to trace it in all its ramifications ; the minute 

 branches of the nerves of the human body are, not only 

 invisible to the naked eye, but even to the most acute 

 observer when assisted by the magnifying power of the 

 microscope, but we are certain that they do exist, from 

 the pain we feel when they are injured. Until lately, 

 the Infusoria^ those microscopic animals that are found 

 in infusions of vegetable substances in water, were sup 

 posed to be possessed of neither nerves nor stomach, and 

 to be fed by absorption ; but the ingenious experiments 

 of a learned foreigner have proved, that, instead of being 

 M'ithout a stomach, they are provided with as many as 

 five or six: it is true, that the nerves have not yet been 

 detected, but we have a right to infer their existence 

 from their effects ; so that these minute creatures, which 

 we have been accustomed to consider as nearly destitute 

 of organs, are, in fact, beautifully formed, and as perfect 

 in their kind as any other of the Creator's works. 



The second Division of the objects of natural history, 

 namely, the Invertebral animals, which we have now 

 to describe, are placed by themselves, on account of their 

 being without an internal skeleton, consisting of a series 

 of vertebra?, or bones of the back. This distinction is ex- 

 plained in the introductory chapter to the Book of Ani- 

 mals. They have been separated, by Lamarck, into 

 Eleven Classes, namely: — 



1. "^lox-iAj sex, {soft-bodied animals,) \\\ general covered with a 

 shell ; as, for instance, a snail : or without a shell, as a 



slug. m;^. 



C^l 



