14 



DIGESTION. 



indeed be received as a very general rule that a 

 certain quantity of matter, which in itself 

 contains but a small proportion of the princi- 

 ples which immediately serve for nutrition, is 

 necessary for the due performance of the func- 

 tions of the stomach, probably in some degree 

 for the purpose of mere dilution or mechanical 

 division. The same remark applies to sugar 

 as to oil. Sugar would appear to be one of 

 the most nutritive of the proximate principles, 

 but when taken alone or in too great quantity 

 it deranges the digestive organs, and becomes 

 incapable of supporting life.* 



The difference in the different kinds of ali- 

 ment between their capacity of affording the 

 materials from which chyme may be produced, 

 and the facility with which they are acted upon 

 by the stomach, or in ordinary language, be- 

 tween their nutritive and their digestible quality, 

 has been distinctly recognized by various phy- 

 siologists,! although it has not always been 

 sufficiently attended to. We have some strik- 

 ing illustrations of the fact in a series of expe- 

 riments which were performed by Goss,J and 

 in those of Stark , where the digestibility and 

 the nutrition of various species of aliment bore 

 no relation to each other, while they afford the 

 most decisive proof of the advantage, or rather 

 the necessity, of a mixture of substances, in 

 order to produce the compound which is the 

 best adapted for the action of the stomach. 



We have referred above to the difference in 

 the digestive powers of the stomachs of diffe- 

 rent classes of animals as depending on their 

 peculiar organization. In many instances the 

 difference is so strongly marked as to leave no 

 doubt either as to its existence or as to the 

 cause by which it is directly produced. But 

 there are many cases where we observe the 

 effect without being able to assign any imme- 

 diate cause for it ; where substances, which are 

 highly nutritive and perfectly salutary to certain 

 individuals, are apparently incapable of being 

 digested by others. After making all due al- 

 lowance for the effects of habit, association, 

 or even caprice, there still appears sufficient 

 ground for concluding that there are original 

 differences in the powers of the stomach, which 

 cannot be assigned to any more general prin- 

 ciple. This observation applies principally to 

 the individuals of the human species, where 

 such variations, or, as they have been termed, 

 idiosyncrasies, of all descriptions are much 

 more apparent than in any other kind of ani- 

 mals. All other animals, even those which 

 the most nearly resemble the human species, 

 are much more uniform in this respect, being 

 guided in the choice of their food principally 

 by that instinctive feeling which leads them 



he found that animals could not be fed upon pure 

 sugar, oil, or gum ; Physiol. t. ii. p. 390, and Ann. 

 China, et Phys. t. iii. p. 66 et seq. ; see Bos- 

 tock's Physiol. v. ii. p. 467, 8. 



* Haller, El. Phys. xix. 3. 12; Stark's Works, 

 p. 94 et alibi; Pearson's Synopsis, p. 104, 5. 



t Adelon et Chaussier, Diet. Sc. Med. Art. 

 " Digestion," t. ix. 



J Spallanzani, Sur la Digestion, par Senebier, 

 p. cxxxi...cxl. 



Works, p. 89 et seq. 



to select the substances which are the best 

 adapted for their organs. But even here we 

 meet with cei tain peculiarities, where animals 

 prefer certain kinds of aliment, and where 

 there is no obvious anatomical or physiological 

 cause which can explain the effect. This, 

 however, we may regard as an exception to the 

 general rule, for there is perhaps no one of the 

 functions in which we are enabled more clearly 

 to trace the adaptation of the organ to the struc- 

 ture and habits of the animal, than in what 

 respects the supply of nutrition, including the 

 mode of procuring the food, and the whole of 

 the series of changes which it experiences from 

 the digestive organs.* 



Liquids of various kinds constitute an im- 

 portant part of the diet of almost all indivi- 

 duals. They may be arranged under the two 

 divisions of those liquids which we employ 

 merely for the purpose of quenching thirst, or 

 diluting our solid food, or such as are made 

 the vehicles of nutriment, including various 

 kinds of decoctions and infusions. The latter 

 are derived both from the animal and the vege- 

 table kingdoms, and when duly prepared form 

 a species of food, which, as containing the 

 most soluble and the most sapid portions, is, 

 in most cases, both highly nutritive and diges- 

 tible. But we observe here the same kind of 

 idiosyncrasy to which we referred above, and 

 which it frequently becomes necessary to attend 

 to in the directions that are given respecting 

 diet, and more especially to invalids and to 

 children. 



The liquids that are employed for the pur- 

 pose of quenching thirst, which are more pro- 

 perly styled drinks, may be arranged under the 

 two heads of vegetable infusions or decoctions 

 and fermented liquors. Of the former a great 

 variety have been employed in different coun- 

 tries and at different periods, but in Europe, 

 almost the only kinds which are in common 

 use are tea and coffee. These cannot be con- 

 sidered as in themselves affording any nourish- 

 ment, but they are generally employed with the 

 addition of some nutritive substance, and if not 

 taken in excess, would appear to promote 

 digestion, and to exercise a favourable influence 

 on the system at large. 



It has been observed that all tribes of people 

 that have made the least advances in the arts 

 of life, either by accidental observation or by 

 tradition, have become acquainted with the 

 process of fermentation, and have indulged in 

 the use of certain species of vinous liquors. 

 The making of wine is among the first transac- 

 tions that are recorded of Noah after he left the 

 ark, and the experiment which he made of its 

 effects has been but too frequently repeated by 

 his progeny. The basis of all vinous liquors 

 being the saccharine principle, the grape has 

 been naturally had recourse to in all those parts 

 of the world which are adapted to the growth 

 of the vine ; in the more northern regions, as 

 in our own island, different species of grains 

 are employed, in which the sugar is evolved by 

 an artificial process, while in the torrid zone, 



* Bostock's Physiol. v. ii. p. 469, 70. 



