NATURE AND DESTINATION OF FOOD. 103 



Bischoffand Voit,' when taken in conjunction with the inquiries of the com- 

 missioners appointed to investigate the subject in Paris and Amsterdam, 2 

 appear to have established that, though gelatin is not destitute of nutritive 

 value, it cannot permanently replace albumen as an article of diet. For a 

 short period it may indeed be serviceably, perhaps even advantageously em- 

 ployed ; and the nutritive value which experience has long assigned to soups 

 and broth, whilst partly attributable to the albuminous matters which they 

 hold in solution, may also in some measure be due to the readiness with 

 which their gelatinous constituents can be absorbed and applied to the pur- 

 poses of nutrition and calorification. The very large quantity of gelatin 

 which Bischoff and Voit found it necessary to make their dog consume in 

 order to maintain its weight a quantity of dry gelatin, in fact, equal to the 

 weight of moist flesh on which the animal was ordinarily fed is worthy of 

 particular notice, and furnishes an explanation of the negative results which 

 were obtained by previous inquiries. 3 That it rapidly undergoes a decom- 

 position analogous to that of the albuminous compounds, is evident from 

 the observations of Frerichs on the result of the ingestiou of large quan- 

 tities of pure gelatin : this being a marked increase in the proportion of 

 urea in the urine, with an elevation of its specific gravity from 1018 to 1030 

 or even 1034. It is very interesting to remark (with Dr. Prout) that, in the 

 only instance in w ? hich Nature has provided a single article of food for the 

 support of the animal body, she has mingled articles from the first three of 

 the preceding groups. This is the case in Milk, which contains a consider- 

 able quantity of albuminous substance, casein, which forms its curd ; a good 

 deal of oily matter, the butter; and no inconsiderable amount of sugar, 

 which is dissolved in the whey. The proportions of these vary in different 

 Mammalia, and they depend in part upon the nature of the food supplied to 

 the Animal that forms the milk ; but the substances are thus combined in 

 every instance. 



62. Up to a comparatively recent period, attempts were made to divide 

 all kinds of food, in accordance with their supposed application in the body, 

 into two great classes, called respectively the "histogenetic" or tissue-form- 

 ing, and the "respiratory" or heat-producing aliments. It was imagined 



1 Gesetze der Ernahrung, 1860, p. 215. 



2 See the Report of the French Gelatin Commission, in the Compt. Rend., Aout, 

 1841 ; that of the Amsterdam Commission in Het. Institut, No. 2, 1843; Gazette 

 Medicale, Mars 16, 1844; Voit's paper in the Zeitschrift fur Biologie, Band viii, 

 1872, p. 297 ; and Etzinger in idem, Band x, p. 84. 



3 That Gelatin is not destitute of nutritive value is shown by the fact that in one of 

 Bischoffand Voit's experiments a dog, weighing about 80 Ibs., lost in four days one 



when given in considerable quantities, will -not support life, is shown by the results 

 of another experiment, in which a dog weighing over 50 Ibs. died on the 31st day 

 when supplied with 3088 grains of gelatin, 2316 grains of starch, 1544 grains of fat, 

 nd 185 grains of flesh extract. Etzinger has recently shown (Zeits. f. Biologie, B. 

 x) that ligament, cartilage, and bone, are all largely soluble, with loss of their gela- 

 tinifying power, in gastric juice, and are all capable of absorption. Liebig's essence 

 of meat contains from 16-21 per cent, of water, 18-'_'2 per cent, of ash, and 56-60 

 per cent, of substances soluble in alcohol of 80 per cent, strength (Tluidichum, On 

 the Origin, Nature, and Uses of Liebig's Extract <>f Meat, Pamphlet, 1869) and 

 no gelatin or fat. In regard to the physiological action of beef tea and the extract 

 of meat, the reader may refer to the pamphlets on this subject by Kemmerich, Bel- 

 jawsky, Bogoslowsky (Centralblatt, f. d. Med. Wiss., No 32, 1871, and Archiv f. 

 Anat. v. Phys., 1872), and to Bunge (Cbl., 1871, p. 636). Kemmerich attributed 

 these good effects to the influence of the alkaline salts they contain exclusively, a view 

 that is not supported by the results of experiments performed by other observers. 



