98 CHEMICAL COMPOSITION OP THE BODY. 



the mixture with water, filtering, acting on the residue with ether and alcohol, 

 and evaporating, pure stercoriu may be obtained. It resembles cholesteriu in 

 many points, and is believed to proceed from that substance. Its crystalline 

 form is, however, different, and it fuses at a lower temperature 96.8 Fahr. 

 About ten grains are eliminated per diem. 



57. INORGANIC COMPOUNDS. The principal inorganic compounds that 

 form part of the tissues and fluids of the body, are water, carbonic acid, and 

 ammonia; the carbonates, chlorides, sulphates, and phosphates of the alka- 

 lies and alkaline earths, and potassium sulphocyanide. Water is the most 

 widely distributed of all the constituents of the body, and forms rather more 

 than half its weight (59 per cent.), the different tissues, however, containing 

 very various amounts, from the enamel of the teeth, which has only 2 per 

 1000, to the renal tissue, which has 827 per 1000. Fat contains 209 per 

 1000 ; the tissues of the liver 693 ; of the spinal cord, 697 ; of the skin, 720 ; 

 of the brain, 750; of the muscles, 757; of the spleen, 758; of the thyrnus, 

 770; of the nerves, 780 ; and the heart, 792 parts in 1000. It is for the 

 most part directly ingested, but a small portion is probably also found in the 

 body, as one of the terminal products of the various chemical changes un- 

 dergone by the more complex substances used as food. It is discharged from 

 the body by the kidneys, skin, lungs, and bowels. It confers elasticity, ex- 

 tensibility, and transparency on the several tissues. It is a general solvent, 

 and is essential for all processes of imbibition, diffusion, and of movement in 

 general, both in a chemical and physical sense. By its evaporation, a large 

 amount of heat is rendered latent, and it hence serves as the chief heat regu- 

 lator of the body. The physiological significance of the various saline con- 

 xtifneuts, except in so far as they form part of the bony skeleton, has not 

 been satisfactorily ascertained, though in some instances, it is probable they 

 serve to retain in solution some of the organic compounds. With the ex- 

 ception of common salt, they are rarely taken into the body in their chemi- 

 cally pure state, being usually combined with the organic constituents of 

 the food, and are no less important than these in the general processes of 

 nutrition. In some few instances, they appear to be formed in the body, as 

 in the case of the alkaline sulphates and phosphates, the former of which, 

 whilst partially consumed with the food, are in part derived from the oxida- 

 tion of the sulphur contained in the albuminous compounds, whilst the latter 

 in part proceed from the oxidation of phosphorus in organic compounds. 

 The saline compounds are eliminated for the most part unaltered by the kid- 

 neys and bowels. The chief exceptions to this rule are found in the salts 

 of the vegetable acids as the tartrates, malates, and citrates, which un- 

 dergo decomposition in the blood, and are discharged in the condition of 

 carbonates. The most widely distributed, as well as perhaps the most im- 

 portant salt in the body is sodium-chloride, or common x<tlt. The blood con- 

 tains rather more than 4 parts of it in 1000, and the proportion undergoes 

 but little variation, whether an excess or a deficiency be ingested with the 

 food in the one case the superfluous quantity being quickly eliminated by 

 the urine, and in the other, the system retaining its hold of the salt with 

 such pertinacity that the quantity discharged falls to a minimum, or its 

 elimination is altogether arrested. Dr. Broadbent 1 has pointed out that this 

 retention can only be in virtue of a special chemical relation between the 

 salt and the animal tissues and fluids, and it is in consequence of such affinity 

 that it, as well as other salts, are of service in the organic processes. It is 

 present in considerable quantity in chyle, lymph, and white of eggs; in the 



1 An Attempt to apply Chemical Principles in Explanation of the Action of 

 Remedies and Poisons. 18G9. 



