651 



that enter into the composition of animated be- 

 ings, and which alone appear fitted to maintain 

 what we may call the chemical movement of 

 vitality. 



We must not confound the sensations of hun- 

 ger with that vague feeling of debility, which is 

 produced by want of nutrition, and by other 

 pathologic causes. The sensation of hunger 

 ceases long before digestion takes place, or the 

 chyme is converted into chyle. It ceases either 

 by a nervous and tonic impression exerted by the 

 aliments on the coats of the stomach ; or be- 

 cause the digestive apparatus is filled with sub- 

 stances, that excite the mucous membranes to 

 an abundant secretion of the gastric juice. To 

 this tonic impression on the nerves of the sto- 

 mach the prompt and salutary effects of what 

 are called nutritive medicaments may be attri- 

 buted, such as chocolate*, and every substance 

 that gently stimulates and nourishes at the same 

 time. It is the absence of a nervous stimulant, 

 that renders the solitary use of a nutritive sub- 

 stance (of starch, gum, or sugar, (less favour- 

 able to assimilation, and to the reparation of the 

 losses, which the human body undergoes. Opi- 

 um, which is not nutritive, is employed with 



* Polit, Essay on New Spain, vol. ii, p. 365. Meat roast- 

 ed, or much broiled, is more stimulating than boiled meat. 

 The manner of preparing food changes it's chemical propor- 

 tions. 



