500 "HYSiOLimY or UUJTGEB. 



physiological phenomena prove that a temporary cessation 

 of 'hunger may be produced though the substances that aro 

 submitted to the organs of digestion may not be, properly 

 speaking, nutritive. The earth of the Ottomacs, composed 

 of alumine and silex, furnishes probably nothing, or almost 

 nothing, to the composition of the organs of man. These 

 organs contain lime and magnesia in the bones, in the 

 lymph of the thoracic duct, in the colouring matter of the 

 blood, and in white hairs ; they afford very small quantities 

 of silex in black hair; and, according to Vauquelin, but 

 a few atoms of alumine in the bones, though this is con- 

 tained abundantly in the greater part of those vegetable 

 substances which form part of our nourishment. It is not 

 the same with man as with animated beings placed lower 

 in the scale of organization. In the former, assimilation is 

 exerted only on those substances that enter essentially into 

 the composition of the bones, the muscles, and the medul- 

 lary matter of the nerves and the brain. Plants, on the 

 contrary, draw from the soil the salts that are found acci- 

 dentally mixed in it ; and their fibrous texture varies 

 according to the nature of the earths that predominate in 

 the spots which they inhabit. An object well worthy of 

 research, and which has long fixed my attention, is the 

 small number of simple substances (earthy and metallic) 

 that enter into the composition of animated beings, and 

 which alone appear fitted to maintain what we may call the 

 chemical movement of vitality. 



We must not confound the sensations of hunger 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, because the digestive appa- 

 ratus is filled with substances that excite the mucous mem- 

 branes to an abundant secretion of the gastric juice. To 

 this tonic impression on the nerves of the stomach the 

 prompt and salutary effects of what are called nutritive 

 medicaments may be attributed, such as chocolate, and 

 every substance that gently stimulates and nourishes at 

 the same time. It is the absence of a nervous stimulant 



