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g-trong doses, act as most violent poisons; they forcibly resist the diges- 

 tive powers, and furnish them nothing to be acted upon, while mild and 

 inert substances yield to these powers, and come under the class of ali- 

 ments. What then is to be thought of our ptisans, of chicken and veal 

 broth, and other such remedies? That they are employed to deceive the 

 hunger and thirst of the patient, to prevent his receiving into his stomach, 

 substances whose laborious digestion would take up the strength requir- 

 ed for the cure of the disease; that they are mere precautions'of regimen, 

 that he who most varies this kind of resource, can only be said to adopt 

 a treatment of expectation, leaving to nature alone, the care of exciting 

 those salutary motions which are to bring about a cure. Why do cer- 

 tain vegetable purgatives, as manna and tamarinds, produce so little ef- 

 fect, even though given in large doses? Because these substances contain 

 many nutritious particles capable of being assimilated, so that strong 

 constitutions digest them, and completely neutralize their irritating or 

 purgative qualities. An animal or vegetable substance, though essential- 

 ly nutritious, may act as a medicine, or even as a poison, when, in con- 

 sequence of the extreme debility of the digestive tube, or because it has 

 not been sufficiently divided by the organs of mastication* it resists the 

 digestive action. Thus surfeits are brought on because the stomach is 

 debilitated, because it is oppressed by too great a mass of substances, or 

 because, having been imperfectly triturated, they are insoluble. It is in 

 considerations of this kind, that the true foundations of materia medica 

 are laid. 



Mineral substances are of a nature too heterogeneous to our own, to ad- 

 mit of being converted into our substance. It appears that their elements 

 require the elaboration of vegetable life; hence, it has been justly ob- 

 served, that plants are laboratories in which nature prepares the food of 

 animals. 



Aliments obtained from plants are less nutritious than those furnished 

 by the animal kingdom, because in a given bulk, they contain fewer parts 

 that can be assimilated to our own substance. Of all the parts of vegeta- 

 bles, the most nourishing is their amylaceous fecula, but it yields the 

 more readily to the action of the digestive organs, from having already 

 experienced an incipient fermentation ; on that account, leavened bread 

 is the best of vegetable aliments. The flesh of young animals is less 

 nourishing than that of the full grown, although, at an early age, the flesh 

 of the former abounds more in gelatinous juice's; for, this abundant gela- 

 tine wants the necessary degree of consistence. 



However various our aliments may be, the action of our organs always 

 separates from them the same nutritious principles ; in fact, whether we 

 live exclusively on animal or vegetable substances, the internal composi- 

 tion of our organs does not alter; an evident proof, that the substance 

 which we obtain from aliments, to incorporate with our o\\n, is always 

 the same, and this affords an explanation of the saying of the father of 

 physic, " There is but one food, but there exist several forms of food," 



Attempts have been made to ascertain the nature of this alimentary 

 principle, common to all nutritive substances, and it is conjectured, with 

 some probability, that it must be analogous to gummy, mucilaginous, or 

 saccharine substances ; they are all formed from hydrogen and carbon, are 

 well known to differ chemically only in the different proportions of oxy- 

 gen which they contain. Thus, sugar is a kind of gum, containing a con- 

 siderable quantity of oxygen; and which is reduced, in a certain degree, 



K 



