ACTION OF THE LARGE INTESTINE. 619 



that exist in oats, water, or air ; the only substances to which the fowl 

 had access; and that silica must enter into its composition, as a part 

 had disappeared. Before, however, we adopt these conclusions, the 

 experiments ought to be repeated more than once. The chicken should 

 be fed on oats some time before the excrements and shells are subjected 

 to analysis; as the carbonate of lime, and the excess of phosphate de- 

 tected on analysis, might have proceeded, not only from the food, but 

 from earthy matters previously swallowed. Care should also be taken, 

 that it has no access to any calcareous earth ; and we must be certain, 

 that it has not diminished in weight; as, in such case, the earth may 

 have been supplied from its own body. These precautions are the more 

 requisite, seeing, that experiments have shown, that certain birds cannot 

 produce eggs unless they have access to calcareous earth. 



There are some very remarkable instances of chemical changes, in 

 mysterious actions, more immediately concerned in the decomposition 

 and renovation of the frame ; or, in what has been abstractedly termed 

 the function of nutrition. Dr. Henry 1 has announced, that the follow- 

 ing substances have been satisfactorily proved to exist in healthy urine; 

 water, free phosphoric acid, phosphate of lime, phosphate of mag- 

 nesia, fluoric acid, uric acid, benzoic acid, lactic acid, urea, gelatin, 

 albumen, lactate of ammonia, sulphate of potassa, sulphate of soda, 

 fluate of lime, chloride of sodium, phosphate of soda, phosphate of 

 ammonia, sulphur, and silex; yet we have no proof that these sub- 

 stances are obtained from any other source than the food; and some of 

 them are with difficulty obtained any where. Every one of them is 

 necessary for the constitution of the urine ; and many must be formed by 

 a chemical union of their elements under the vital agency. Some are 

 met with in the animal body exclusively. Berzelius 2 found, in 100 parts 

 of human fseces: water, 73*3 ; unaltered residue of animal and vege- 

 table substances, 7*0; bile, 0-9; albumen, 0-9; peculiar extractive mat- 

 ter, 2*7; substance, formed of altered bile, resin, animal matter, &c., 

 14; salts, 1-2. Seventeen parts of these salts contained, of carbonate 

 of soda, 5; chloride of sodium, 4; sulphate of soda; 2 ; ammoniaco-mag- 

 nesian phosphate, 2 ; phosphate of lime, 4. The excrements have like- 

 wise been examined by MM. Leuret and Lassaigne, and others ; but 

 none of the analyses have shed much light on the physiology of digestion. 

 Analyses of the ashes of firm human fseces by Enderlin 3 yielded the 

 following results: chloride of sodium and alkaline sulphate, 1-367; 

 tribasic phosphate of soda, 2-633 ; phosphate of lime, and phosphate 

 of magnesia, 81-372 ; phosphate of iron, 2-091 ; sulphate of lime, 4-56 ; 

 silica, 7-97. 



In the large intestine, gases are met with, along with the faeces. 

 These were examined by MM. Magendie 4 and Chevreul in the three cri- 

 minals already referred to (page 599). The results accord with those 

 of Jurine, 5 obtained long ago, as regards the nature of the gases; but 



1 Elements of Chemistry, 9th edit., ii. 435, Lond., 1823. 



2 Traite de Chimie, trad, par Jourdan et Esslinger, torn, vii., and Simon's Animal Che- 

 mistry, Sydenham Society edit., ii. 372, Lond., 1846, or Amer. edit., Philad., 1846. 



3 Annalen der Chemie und Pharmacie, Mars, 1844, cited by Mr. Paget, Brit, and For.Med . 

 Rev., Jan, 1845, p. 277. 



4 Precis, &c., ii. 126. . Memoir, de la Soc. Royale de Med., x. 72. 



