NATURE AND DESTINATION OF FOOD. 375 



ducing ideo-motor actions, or through ideas with which feelings are associated, 

 and thus producing emotional movements. 



394. Another division of the Nervous System appears to have for its object 

 to combine and harmonize certain muscular movements immediately connected 

 with the maintenance of Organic life } and to bring these into relation with cer- 

 tain conditions of the mind. There is further reason to believe that it also in- 

 fluences, and brings into connection with each other, the processes of Nutrition, 

 Secretion, &c. ; though these, like the muscular movements just mentioned, are 

 essentially independent of it. This portion of the nervous apparatus is commonly 

 known under the name of the Sympathetic system ; it has a set of ganglionic 

 centres and nerves of its own j but it is also intimately blended with the Cerebro- 

 spinal system, receiving fibres from it, and also sending fibres into it. 



395. With reference to that class of operations of which the Cerebrum is the 

 instrument, it is well here to explain that, though the Physiologist speaks of the 

 intellectual powers, moral feelings, &c., as functions of the Nervous System, they 

 are not so in the sense in which the term is employed in regard to other opera- 

 tions of the bodily frame. In general, by the function of an organ, we under- 

 stand some change which may be made evident to the senses, as well in our own 

 system, as in the body of another. Sensation, Thought, Emotion, and Volition, 

 however, are changes imperceptible to our senses by any means of observation 

 we at present possess. We are cognizant of them in ourselves, without the 

 intervention of those processes by which we observe material changes external 

 to our minds ; but we judge of them in others, only by inferences founded on 

 the actions to which they give rise, when compared with our own. When we 

 speak of sensation, thought, emotion, or volition, therefore, as functions of the 

 Nervous System, we mean only that this system furnishes the conditions under 

 which they exist in the living body ; and we leave the question entirely open, 

 whether the "VVM has or has not an existence independent of that of the material 

 organism, by which it operates in Man, as he is at present constituted. 



CHAPTER VII. 



OF FOOD, AND THE DIGESTIVE PROCESS. 



1. Of Food, its Nature and Destination. 



396. THE substances which are required by Animals for the development and 

 maintenance of their fabric, are of two kinds : the Organic and the Inorganic. 

 The Organic alone are commonly reckoned as aliments ; but the latter are really 

 not less requisite for the sustenance of the body, which speedily disintegrates, if 

 the attempt be made to support it upon any organic compounds in a state of 

 purity. In all ordinary articles of diet, however, the Inorganic matters are 

 present in the requisite proportion ; and hence they have very commonly escaped 

 notice. The nature of these substances, and the mode in which they are intro- 

 duced into the body, have been already treated of (CHAP. n. SECT. 6). 



397. The Organic compounds usually employed as food by Man, are partly 

 derived from the Animal, and partly from the Vegetable kingdom; and they 

 may be conveniently arranged under the four following heads: 1 1. The Saccha- 



1 Dr. Prout's classification of alimentary substances is here adopted, with a slight modi- 

 fication; not as being altogether unexceptionable, but as being, in the Author's opinion, the 

 most convenient hitherto proposed. 



