ANIMALS AND VEGETABLES. 45 



confined to certain organs, and certain conditions of these 

 organs. If the nerves of the finger are cut across or 

 compressed, I am unable to communicate to rny finger the 

 requisite power. Sensation has ceased, and along with 

 it, voluntary motion. In the one case, the sensation, by 

 the ligature or division of the nerve, is prevented from as- 

 cending ; in the other, the excitement to voluntary motion 

 is prevented from descending, by the interposition of the 

 same means. I conclude, therefore, that the presence of 

 the nerves is essentially necessary to voluntary motion. 

 Here, however, there is another condition necessary. The 

 organs to which the nerves proceed, must be so construct- 

 ed as to admit of motion. My fingers possess this requisite 

 qualification in an eminent degree ; but when many other 

 parts of my body are touched by any object, even though I 

 feel its presence, I cannot move away the part without a ge- 

 neral movement of the whole body. In many cases, I cannot 

 even accomplish my object by any movement of the body, as 

 when the substance is situated in some central part, so con- 

 structed as not to obey the will, as is the case with gouty 

 or urinary concretions. Voluntary motion, then, depends 

 on the presence of nerves, and the structure of the parts to 

 which these are distributed. 



As all animals may be considered as possessing nerves, 

 and consequently, the essential requisite of voluntary mo- 

 tion ; the organs of animals are likewise so constructed, 

 as to admit of its display in the variety of actions which 

 they perform. In a few animals, however, such as the 

 sponge, the displays of this power are scarcely discernible. 

 But as in all such animals there are some soft parts, and 

 as they all possess nerves, we may infer from analogy the 

 existence of this faculty, although its operations are imper- 

 ceptible to our senses. 



