430 NUTRITION ANIMAL HEAT AND FORCE. 



testines is composed chiefly of nitrogen, with hydrogen and carburetted 

 hydrogen in about equal proportions (five to eleven parts per hundred), and 

 but a trace of hydrogen monosulphide. With the exception, then, of oxy- 

 gen and carbon dioxide, the latter being an excretion, the gases do not hold 

 an important place among the constituents of the organism. At all events, 

 their uses, whether they be important or not, are but little understood. 



Water. Water exists in all parts of the body ; in the fluids, some of 

 which, as the lachrymal fluid and perspiration, contain little else, and in the 

 hardest structures, as the bones and the enamel of the teeth. In the solids 

 and semi-solids it does not exist as water, but it enters into their composition, 

 assuming the consistence by which the tissues are characterized. 



The quantity of water which each organic substance contains is impor- 

 tant ; and it is provided that this quantity, though indefinite, shall not ex- 

 ceed or fall below certain limits. All organs and tissues must contain a tol- 

 erably definite quantity of water to give them proper consistence. The 

 effects of too great a proportion of water in the system are well known to 

 physicians. General muscular debility, loss of appetite, dropsies and various 

 other indications of imperfect nutrition are among the results of such a con- 

 dition ; while a deficiency of water is immediately made known by the sensa- 

 tion of thirst, which leads to its introduction from without. 



The fact that water never exists in any of the fluids, semi-solids or solids 

 without being combined with inorganic salts, especially sodium chloride, 

 one reason why its proportion in various situations is nearly constant. The 

 presence of these salts influences, in the semi-solids at least, the quantity 

 water entering into their composition, and consequently it regulates thei 

 consistence. The nutrient fluid of the muscles during life contains wat 

 with just enough saline matter to preserve the normal consistence of the 

 parts. This .action of saline matters is even more apparent in the case 

 the blood-corpuscles. If pure water be added to the blood, these bodic 

 swell up and are finally dissolved ; while on the addition of a strong solutioi 

 of salt, they lose water and become shrunken and corrugated. Their nat 

 ural form and consistence can be restored, however, even after they have 

 been completely dried, by adding water containing about the proportion 

 salt which exists in the blood-plasma. It seems clear, then, that water is 

 a necessary part of all tissues and is especially important to the proper con- 

 stitution of organic nitrogenized substances ; that it enters into the constitu- 

 tion of these substances, not as pure water, but always in connection wit! 

 certain inorganic salts ; that its proportion is confined within certain lim- 

 its ; and that the quantity in which it exists, in organic nitrogenized sul 

 stances particularly, is regulated by the quantity of salts which enter, witl 

 it, into the constitution of these substances. 



The quantities of water which can be driven off by a moderate temper 

 ture (212 Fahr.. or 100 C.), from the different fluids and tissues of the 

 body, vary of course very considerably according to the consistence of the 

 parts. The following is a list of the quantities in the most important fluic 

 and solids (Robin and Verdeil) : 



