500
PHYSIOLOGY OF HUNGER.
physiological phenomena prove that a temporary cessation o f hunger may be produced though the substances that are submitted to the organs o f digestion may not be, properly speaking, nutritive. T h e earth o f the Ottomacs, c o m p o s e d o f alumine and silex, furnishes probably nothing, or almost n o t h i n g , t o the c o m p o s i t i o n o f the organs o f man. These organs contain lime and magnesia in the bones, in the lymph o f the thoracic duct, in the c o l o u r i n g matter o f the b l o o d , and in white hairs; they afford very small quantities o f silex in black h a i r ; and, according to Vauquelin, b u t a few atoms o f alumine in the bones, though this is c o n tained abundantly in the greater part o f those vegetable substances which form part o f o u r nourishment. I t is n o t the same with man as with animated beings placed lower in the scale o f organization. In the former, assimilation is exerted o n l y o n those substances that enter essentially into t h e c o m p o s i t i o n o f the b o n e s , t h e muscles, and the m e d u l lary matter o f the nerves a n d the brain. Plants, o n the contrary, draw from the soil the salts that are found accidentally mixed in it ; and their fibrous texture varies according to the nature o f the earths that predominate in the spots which they inhabit. A n o b j e c t well worthy o f research, and which has l o n g fixed m y attention, is t h e small n u m b e r o f simple substances (earthy and metallic) that enter into the composition o f animated beings, and which alone appear lilted to maintain what, we may call the chemical movement o f vitality. W e must not confound the sensations o f hunger with that vague feeling o f debility which is produced by want o f nutrition, and by other pathologic causes. The sensation o f hunger ceases long before digestion takes place, o r the c h y m e is converted into chyle. It ceases either by ft nervous and tonic impression exerted b y the aliments o n the coats of the stomach ; or, because the digestive apparatus is filled with substances that excite the mucous membranes to an abundant secretion o f the gastric juice. To this tonic impression on the nerves o f the stomach the prompt and salutary effects of what are called nutritive medicaments may be attributed, such as chocolate, and e v e n substance that gently stimulates and nourishes at the same time. It is the a b s e n c e o f a nervous stimulant