NUTRITION. 7 



The ORGANS OF NUTRITION occupy the greater part of the space between the 

 diaphragm and the lower limbs, and are composed of the following parts. The mouth 

 receives and, in most cases, grinds the food until it is sufficiently soft to be passed 

 onwards into the general receptacle, called the stomach. Here begins the process of 

 digestion, which is chiefly carried on by means of a liquid called the gastric juice, which 

 is secreted by glands within the stomach, and dissolves the food until it is of an uni- 

 form soft consistency. In this state the food is called " chyme," and passes from the 

 stomach into a tube called the " duodenum." Here the chyme begins to separate 

 into two portions ; one, an indigestible and useless mass, and the other, a creamy kind 

 of liquid, called " chyle." The former of these substances is propelled through the 

 long and variously-formed tube, called the intestinal canal, and rejected at its outlet ; 

 while the chyle is taken up by numerous vessels that accompany the intestines, and is 

 finally thrown into one of the large veins close by the heart, and there mixes with the 

 blood. 



There is another curious system called the u lymphatic," on account of the limpid 

 appearance of the liquid which is conveyed through the lymphatic vessels. These are 

 analogous to the lacteals, but instead of belonging to the intestines, they are spread 

 over the whole frame, being thickly arranged just under the skin. They are curiously 

 shaped, being studded with small knotty masses, and fitted with valves which keep 

 the contained liquid in its proper course. Both the lacteal and lymphatic vessels pour 

 their contents into one large trunk, called from its position the thoracic duct. This 

 vessel is about twenty inches in length, and when distended, is in its widest part as 

 large as a common lead-pencil. 



Al] these wonderful forms and organs would, however, be but senseless masses of 

 matter, differing from each other by the arrangement of their component parts, but 

 otherwise dead and useless. It needs that the being which is enshrined in this bodily 

 form (whether it be man or beast) should be able to move the frame at will, and to 

 receive sensations from the outer world. 



More than this. As all vertebrated animals are forced at short intervals to yield 

 their wearied bodies to repose, and to sink their exhausted minds in the temporary 

 oblivion of sleep, there must of necessity be a provision for carrying on the vital 

 functions without the active co-operation of the mind. Were it otherwise, the first 

 slumber of every being would become its death-sleep, and all the higher classes of 

 animals would be extirpated in a few days. The mind would be always on the stretch 

 to keep the heart to its constant and necessary work ; to watch the play of the lungs 

 in regenerating the blood ; to aid the stomach in digesting the food, and the intestinal 

 canal in sifting its contents ; together with many other duties of a character quite as 

 important. 



Supposing such a state of things to be possible, and to be put in practice for one 

 single hour, how terrible would be the result to humanity ! We should at once degen- 

 erate into a mass of separate, selfish individuals, each thinking only of himself, and 

 forced to give the whole of his intellectual powers to the one object of keeping the 

 animal frame in motion. Society would vanish, arts cease from the face of the earth, 

 and the whole occupation of man would be confined to living an isolated and almost 

 vegetable life. 



This being the case with man, the results to the lower portions of the animal king- 

 dom would be still more terrible. For their intellect is infinitely below that of the dull- 

 est of the human race, and they would not even possess the knowledge that any active 

 exertion would be necessary to preserve their lives. And for all living beings the 

 wandering of the mind but for a few seconds would cause instantaneous death. 



All these difficulties are removed, and the animal kingdom preserved and vivified, 

 by means of certain vital organs, known by the name of nerves. 



It is clear enough that mind does not act directly upon the muscles and the various 

 organs of the material body, but requires a third and intermediate substance, by which 

 it is enabled to convey its mandates and to receive information. The necessarily 

 multitudinous channels through which this substance is conveyed are called "nerves," 

 and are of a consistency more delicate than that of any other portions of the animal 



