DIETETICS. 



bute to digestion : hence, in eveiy order 

 of animals, the gastric juice is the princi- 

 pal cause of digestion, and it agrees in 

 every class in many properties, and dif- 

 fers in others. In the frog 1 , the newt, 

 scaly fishes, and other cold animals, it 

 produces digestion in a temperature near- 

 ly equal to that of the atmosphere. In 

 warm animals it is incapable of dissolv- 

 ing the aliment in a degree of heat lower 

 than that of these animals. In warm ani- 

 mals the food is digested in a few hours, 

 whereas in the opposite kind it requires 

 several days, and even weeks, particular- 

 ly in serpents ; likewise, the gastric juice 

 of the gallinaceous class can only dissolve 

 bodies of a soft and yielding texture, and 

 previously triturated; whilst in others, as 

 serpents, the heron, birds of prey, and the 

 dog, it decomposes substances of great 

 tenacity, as ligaments and tendons ; and 

 even of considerable hardness, as the 

 most compact bone : man belongs to this 

 class, but his gastric juice seems to have 

 no action on the hardest kind of bones. 

 Some species likewise are incapable of 

 digesting vegetables, as birds of prey ; 

 but man, the dog, cat, crows, &c. dis- 

 solve the individuals of both kingdoms 

 alike, and are omnivorous, and in general 

 their gastric juices produce these effects 

 out of the body : hence, the dissolving 

 power of this fluid depends on the dif- 

 ference of the, nourishment, and by some 

 authors it has been said to be the cause of 

 hunger, and of the difference in the choice 

 of the particular aliment ; by which pow- 

 er the carnivorous only enjoy flesh ; the 

 granivorous and ruminating, only vegeta- 

 ble aliments, and no flesh ; but man and 

 the omnivorous, both vegetable and ani- 

 mal substances. It is, however, asserted 

 by Carradori, as decided, that nocturnal 

 birds of prey are capable of digesting ve- 

 getables : it results from his experiments, 

 that they also support themselves very 

 well with this nourishment, in spite of 

 their repugnance to it If this be the 

 case, the opinion is erroneous, that the 

 gastric juice of these birds has only an 

 affinity with animal substances ; and what 

 he has established, viz. that carnivorous 

 animals find a nutriment in the products 

 of plants, was already rendered probable 

 by the discovery of Fourcroy, of the ex- 

 istence of gluten, albumen, and gelatin, in 

 the vegetable tribes. Spallanzani, how- 

 ever, proves the insufficiency of Carra- 

 dori's experiments, as the owl died when 

 confined to vegetable food. The time, 

 moreover, requisite for digestion is dif- 

 ferent in different animals ; in many it 



VOL. rv. 



does not exceed five or six hours, and in 

 some it is much shorter. 



From the numerous experiments of 

 Gosse of Geneva upon digestion, and the 

 action which the gastric juice has upon 

 different substances, great light has been 

 afforded us upon this interesting subject. 

 He informs us, that in about one hour 

 and a half after the food is taken into the 

 stomach, it is changed into a pultaceous 

 mass ; the gastric iuicc, likewise, renders 

 it fluid without altering its nature ; and 

 when digestion is properly carried on, 

 there is no appearance of acidity or alka- 

 lescence ; the food does not ferment, and 

 the process of digestion is not completed, 

 until the space of between two and three 

 hours has elapsed. The chyme which 

 arises from aliments taken either from the 

 animal or vegetable kingdom is the same; 

 they both are by the gastric fluid convert- 

 ed into the same substance, which is in 

 consequence, most probably.of their both 

 containing gelatin, &c. : if, however, the 

 digesting solvent is not in sufficient quan- 

 tity, or is in a diseased state, the acetous 

 fermentation will take place in vegetable, 

 and the putrid in animal matter ; hence 

 milk, vegetable matter containing sugar, 

 wine, and even spirits, will degenerate, 

 when left to their spontaneous changes 

 in the stomach, to a very strong acid, and 

 sooner, sometimes, than out of the body, 

 perhaps from the heat, &c. ; all oily sub- 

 stances likewise become rancid, and flesh 

 meat putrid, producing acid and putrid 

 eructations, which is never the case in a 

 state of healthy digestion; whilst, in many 

 animals, the digestion is finished before 

 the acetous or putrid fermentation can 

 begin. 



Substances insoluble, or that were not 

 digested in the usual time in the stomach. 

 Animal substancs: 1. Tendinous parts. 

 2. Bones. 3. Oily or fatty parts. 4. In- 

 durated white of egg. Vegetable sub- 

 stances. 1. Oily or emulsive seeds. 2. 

 Expressed oils of different nuts and ker- 

 nels. 3. Dried grapes, and the skins of 

 fish. 4. Rind of farinaceous substances. 

 5. Pods of beans and pease. 6. Skins of 

 stone fruits. 7. Husks of fruits with 

 grains or seeds. 8. Capsules of fruit with 

 grains. 9. Ligneous stones of fruits. 10. 

 The gastric juice does not destroy the 

 life of some seeds, hence bitter-sweet, 

 hemp, misletoe, and other plants which 

 sometimes gr> w upon trees, arc produc- 

 ed by the means of the excrements of 

 birds, the kernels of the seeds being de- 

 fended from the menstruum by exterior 

 rovering. Substances partly soluble, or 



Z 



