DIGESTION. 



13 



The most important of the proximate prin- 

 ciples employed in diet are fibrin, albumen, 

 oil, jelly, gluten, mucilage, farina, and sugar, 

 to which may be added some others of less 

 frequent occurrence. They are derived, more 

 or less, from almost all the classes of animals 

 and vegetables, and from nearly all their indi- 

 vidual parts, their employment being regulated, 

 in most cases, rather by the facility with which 

 they are procured,and reduced into a form proper 

 to be acted upon by the stomach, than by the 

 quantity of nutritive matter which they con- 

 tain. This is one of those subjects in which 

 \ve have to notice the remarkable effects of 

 habit and custom, both on the functions and 

 the sensations. VVe find whole tribes of people 

 living on a diet, which, to those unaccustomed 

 to it, would be not only in the highest degree 

 unpalatable, but likevvi'se altogether indiges- 

 tible ; while, by the various modes of preparing 

 food, which have been suggested, either by 

 luxury or by necessity, the most intractable 

 substances are reduced into a digestible state.* 



The writers on dietetics have attempted to 

 include all substances that are competent to 

 afford nutrition under a few general principles, 

 of which, as they exist in nature, they are 

 supposed to be composed. Cullen, who may 

 be considered as the first who attempted to in- 

 troduce correct philosophical principles into 

 this department of physiology, reduced them 

 to two, the oily and the saccharine, and endea- 

 voured to prove that all the animal fluids may 

 be referred to these principles.f Magendie, 

 on the contrary, proceeding less upon their 

 chemical composition than upon the forms 

 under which they present themselves, classes 

 alimentary substances under the nine heads of 

 farinaceous, mucilaginous, saccharine, acidu- 

 lous, oily, caseous, gelatinous, albuminous, 

 and fibrinous.]: Dr. Prout, whose views on 

 this subject are marked by his characteristic 

 acuteness, reverts to the mode of Cullen, ad- 

 mitting only of the oily, the saccharine, and 

 the albuminous principles, which three, he 

 conceives, form the " groundwork of all orga- 

 nized bodies. " 



Of animal compounds which are employed 



Stark's works, p. 94, 5 ; see also Lorry, Sur les ali- 

 mens ; Plenk, Bromatologia ; Soemmering, Corp. 

 hum. fab. p. 241, 250; Richerand, El. Phys. 3, 

 p. 83 ; Parr's Diet. art. Aliment; Pearson's Syn- 

 opsis, parti. ; Lawrence's Lect. p. 201, 9 ; Thack- 

 rah's 2d Lect. on Diet, p. 54 et seq. ; Paris 

 on Diet ; Roget's Bridgewater Treatise, part 2, 

 ch. 3, $ 1. 



* Elliotson's Physiol. p. 65,6; Roget, part 2, 

 ch. 3, 1. 



t Physiol. 211, and Mat. Med. v. i. p. 1, ch. 

 1, p. 218 etseq. 



J Physiol. t. ii. p. 3, 4; see also Fordyce on Di- 

 gestion, p. 84 et seq. ; Paris on Diet, part 2, p. 

 117 et seq. ; Richerand, El. Physiol. $ 3, p. 82; 

 Dumas, Physiol. t. i. p. 187 ; Davy's Lect. on Agric. 

 Chem. p. 73 et seq. ; Londe, Diet, de Med. et 

 de Chir. art. " Aliment," t. ii. p. 1 et seq ; Ros- 

 tan, Diet, de Med. art. " Aliment," t. i. p. 523 

 etseq.; Rullier, Ibid. Art. "Nutrition," t. xv. 

 p. 161 et seq. ; Kellie, in Brewster's Encyc. Art. 

 " Aliment." 



Abstract of his Gulstonian Lecture, p. 5, 9. 



in diet milk may be regarded as holding the first 

 place, both from its nutritive and its digestible 

 properties, and as such it has no doubt been 

 provided by nature for the newly-born animal, 

 when it requires a diet, which may be adapted 

 to the delicacy of its organs in its novel state 

 of ex.stence, while, at the same time, it pro- 

 vides for its rapid growth. We accordingly 

 find that the three principles mentioned above 

 are combined in milk in a manner the most 

 proper for this double purpose, and that there 

 is no compound, either natural or artificial, 

 which is equally well suited to it.* Next to 

 milk, with respect to its nutritive properties, 

 we may class eggs of various kinds, the mus- 

 cular fibre of animals, and their gelatinous and 

 albuminous parts, very few of which, how- 

 ever, are employed in diet until they have 

 undergone the various operations of cookery. 

 Of these operations the most important in their 

 dietetical effect is the formation of decoctions 

 or infusions, constituting soups of all descrip- 

 tions, in which we retain the more soluble, 

 and, for the most part, the more nutritive matter, 

 while the residue is rejected. The fish which 

 are usually employed in diet consist of a much 

 greater proportion of jelly and albumen than 

 the flesh of the mammalia and of birds; these 

 principles are united, in most cases, with a con- 

 siderable quantity of oil. 



The most nutritive of the vegetable proximate 

 principles is gluten ; it forms a considerable 

 proportion of certain kinds of seeds, and more 

 especially of wheat, and we accordingly find 

 that in all those countries which admit of the 

 growth of this plant, and which have arrived 

 at any considerable degree of civilization, 

 wheaten bread forms the most important article 

 of vegetable diet, and one which appears the 

 best adapted for all ages and all constitutions. 

 Next to gluten we may rank farina, both from 

 its valuable properties and from the extent to 

 which it is employed. It enters largely into 

 the composition of wheat and of the other 

 seeds of the cerealia, also of rice and maize, 

 while it constitutes a great proportion of the 

 whole substance of the leguminous seeds and 

 of tubers. It also forms the principal in- 

 gredient of the chesnut, and of the esculent 

 algae, so that, upon the whole, we may con- 

 sider it as entering more largely into the aliment 

 of mankind, in all different climates and situa- 

 tions, than any other vegetable compound. 



Perhaps there is no proximate principle 

 which contains in the same bulk a larger pro- 

 portion of nutritive matter than oil, and we 

 accordingly find that oil, as derived either from 

 the animal or vegetable kingdom, enters largely 

 into the diet of all nations. But it affords an 

 example of one of those articles, which, al- 

 though highly nutritious, is not very digestible 

 without a due admixture of other substances, 

 which may in some way render it more proper 

 for the action of the gastric juice. f It may 



* Prout, ut supra, p. 12. 



f It is upon this principle, rather than to the ab- 

 sence of azote, that we should be disposed to account 

 for the results of Magendie's experiments, iu which 



