500 
PHYSIOLOGY Or HTJKGEH. 
physiological phenomena prove that a temporary cessation 
of hunger may he produced though the substances that arc 
submitted to tlie 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 ehocolate, and 
every substance that gently stimulates and nourishes at 
the same time. It is the absence of a nervous stimulant 
