212 On the Anatomy and Physiology of the Organs of the Senses. 



Matter, or that of which the world upon which we are placed is com- 

 posed, is known to us only by the existence of certain properties belonging 

 to it ; and the means, by w'hich we are enabled to appreciate those pro- 

 perties, are called the senses, or rather we should say the physical senses, 

 in contradistinction from our sense of right and wrong, &c. called our 

 moral senses. 



But the actual scope of the senses has been prodigiously over estimated, 

 and a great variety of perceptions, which are conclusions due to reason, 

 have been attributed to the senses. The objects made known to us di- 

 rectly by our senses are few ; their impressions are ratiier data, from which 

 we derive certain inferences, but we forget or neglect the chain of reason- 

 ing, and attribute the inference directly to an impression. Thus the 

 existences of light and heat are spoken of usually as made known to us by 

 the evidence of our senses, whereas they only take cognizance of certain 

 effects of colour or temperature upon different bodies, which are compared 

 together by our reason, which thence draws the inference that light and 

 heat exist abstractedly considered, and distinct from the bodies on which 

 their eEfects have been observed, although it is evident no organ of sense 

 has ever been thus directly impressed by them. Such knowledge is the 

 result of a comparison j that is to say, it is a conclusion of the reason, 

 drawn from data supplied by the memory, and by no means an original 

 perception of sense. 



In the higher animals the senses are five in number, tact, taste, smell, 

 hearing, and sight ; to which have been added, the sensations of heat and 

 cold, that attendant upon the action of a voluntary muscle, and perhaps 

 some others equally specific with any of the former, although their seat is 

 not so well understood. Of these senses, a greater or less number are en- 

 joyed by all organised bodies possessed of animal life, and possibly by a 

 very few others, though in very different degrees of perfection. 



The relative importance of the senses in the oeconomy of the higher 

 animals, will be best seen if we enumerate the other functions with them. 

 These are, the mechanical, chemical, vital, sensorial, and reproductive.* 



Under the first are comprehended the mechanism and leverage of the joints, 

 the various methods of locomotion and prehension, the adaptation of the 

 skeleton to its ends, the production and modulation of the voice, and a 

 variety of other provisions which it is unnecessary to enumerate. 



Under the second, the chemical, are the changes undergone by the at- 

 mosphere during the process of respiration. 



Under the vital, we have the various processes subservient to nutrition ; 

 as digestion, ciiylification, secretion, nervous power, &c. a scries of effects 

 to be referred neither to mechanical nor chemical agency, and called, from 

 their occurrence only in the living body, vital. The fourth set of functions 



* Roget. 



