STOMACH AND INTESTINE. 



389 



dissolved salts, which are by no means in- 

 different to the organism. 



In tlie following cursory view of the ordinary 

 articles of diet, we shall begin by contrasting 

 the general characters of animal and vegetable 

 food. We shall then sketch the chief va- 

 rieties of each generally made use of. Ami, 

 finally, we shall attempt to estimate the pro- 

 portions of each contained in a suitable die- 

 tary of ordinary mixed food. 



It is to animal food that we must on the 

 whole assign the first rank as an article of 

 diet. For not only do the tissues of one 

 animal necessarily contain most, if not all, of 

 the organic and inorganic substances required 

 for the construction of another, and in some- 

 thing like fhe proper proportions of their 

 respective ingredients, but they are generally 

 devoid of all noxious constituents. Besides 

 these advantages, they offer the equally im- 

 portant ones of possessing such a structure, 

 arrangement, and solubility, as materially aid 

 their entry into the organism. Hence they are 

 not only much more nutritious than an equal 

 quantity of vegetable food, but are also di- 

 gested and assimilated with far greater ease 

 and rapidity. It is for this reason that the 

 use of animal food is so much to be preferred 

 in all circumstances where it is our object to 

 avert the speedy exhaustion of the vital powers. 

 Against these advantages, possessed by 

 animal food, we must, however, set off the 

 disadvantages, that it not only contains some 

 substances which (like gelatine and the horny 

 tissues) appear to be either useless or even 

 to require a speedy excretion ; but that, as 

 a rule, it is deficient in those non-azotized 

 elements, which are so important to the main- 

 tenance of the combustion and heat of the 

 organism. For the limited quantity of fatty 

 matters which it generally includes rarely 

 suffices to make these hydrocarbons a proper 

 substitute for the copious amylaceous and 

 saccharine constituents of vegetable food. 



The main disadvantages of vegetable food 

 are equally obvious. It generally contains 

 but a small proportion of the protein com- 

 pounds. And even this limited quantity is 

 often virtually diminished by their insoluble 

 state ; or by the indigestible form which is 

 implied by their mechanical arrangement in 

 the vegetable tissues. Many of its amyla- 

 ceous constituents are also rendered useless 

 in the same way : being enclosed in insoluble 

 envelopes, which effectually shield them from 

 the digestive process; or having a composi- 

 tion which requires to be altered by a chemi- 

 cal metamorphosis before they can be fitted 

 for absorption. These objections can be to 

 a great extent obviated by the ingestion of a 

 larger quantity of such food, as well as by a 

 more protracted sojourn in the alimentary 

 canal. But, besides these disadvantages, the 

 inorganic constituents of certain kinds of 

 vegetable food appear to be insufficient for 

 the replacement of the loss consequent on 

 the waste of the animal. Thus the ash of 

 many esculent vegetables is peculiarly deficient 

 in the important ingredients of soda and the 



chlorides. The poisonous materials con- 

 tained in the tissues of some plants constitute 

 another objection to vegetable diet ; an 

 objection which is, however, generally ob- 

 viated by the instinct of animals, and by the 

 experience of Man, or by the purification 

 which the process of cooking often affords. 



Animal food. The muscular substance, 

 accompanied by more or less of its intersti- 

 tial and investing fat and areolar tissue, forms 

 what is called meat or flesh, in the ordinary 

 acceptation of these words. 



The mechanical subdivision of a mass of 

 meat would of course afford us the micro- 

 scopic elementsof the above tissues; namely, 

 sarcolemma, sarcous substance, white and 

 yellow fibrous elements, fat, and blood 

 vessels ; together with a certain quantity of 

 blood, and of the nutritional fluids which sa- 

 turate each of these textures. Its chemical 

 composition varies, not only with the nature, 

 but also with the age, food, habits, and indi- 

 vidual peculiarities, of the animal yielding it. 

 Hence it is impossible to give any definite 

 account of its quantitative chemistry. We 

 can only enumerate its principal constituents ; 

 and, in the case of some of the more im- 

 portant of them, approximatively estimate 

 their amount. The protein-compound, that 

 forms by far the greater part of the mus- 

 cular fibres, is a substance which possesses 

 characters closely allied to those of fibrin, 

 and has received the name of syntonin. It 

 is usually present in a proportion of. about 

 15 or 16 per cent. The albumen of the 

 juice which soaks the whole muscular mass, 

 and the gelatin which is extracted from it 

 by boiling, may each be estimated at about 

 2 per cent. Its extractive, exclusive of 

 salts, amounts to about 3 per cent. ; of 

 which nearly half is dissolved by alcohol, 

 half by water. This constituent has a very 

 complex composition : osmazom, lactic acid, 

 inosit, kreatin, kreatinin, and a variety of 

 other substances, having been detected in it 

 by the labours of modern chemists. The 

 salts of meat form about ] per cent, of its 

 fresh substance, or about 5 per cent, of its 

 dried mass ; nearly three-fourths of their 

 quantity being phosphates of the alkalies, and 

 two-thirds of the remainder phosphates of the 

 earths, with a little iron. The chlorides of 

 the alkalies are about one-fourteenth of the 

 entire ash. They are remarkably contrasted 

 with the chlorides contained in the ash of the 

 blood, by the great proportion which the 

 chloride of potassium bears to that of sodium. 



It is impossible to estimate the quantity of 

 fat contained in meat as usually eaten. But 

 even after the removal of all visible adipose 

 tissue, Von Bibra has found fractions ranging 

 from one -twentieth to one-filth ; the smaller 

 amounts corresponding to the flesh of the 

 Hare and Deer, while the larger (in the beef of 

 Oxen) were perhaps partially due to a more 

 or less artificial fattening. 



The flesh of Birds contains less water and 

 fat, and more albumen, syntonin, and kreatin, 

 than that of most of the Mammalia hitherto 



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