General Yiew of the Chemical Constituents 



of the Organism. 



247. (A.) Inorganic Constituents. 



I. Water forms 58 '5 per cent, of the whole body, but it occurs in different 

 quantity in the different tissues; the kidneys contain the most water, S2 - 7 per 

 cent.; bones, 22 per cent.; teeth, 10 per cent.; while enamel contains the least, 

 0'2 per cent. 



[ Water is of the utmost importance in the economy, and it is no paradox to say 

 that all organisms live in water, for though the entire animal may not live in 

 water, all its tissues are bathed by watery fluids, and the essential vital processes 

 occur in water (p. 458). A constant stream of water may be said to be passing 

 through organisms, a certain quantity of water is taken in with the food and 

 drink, which ultimately reaches the blood, while from the blood a constant loss is 

 taking place by the urine, the sweat and breath. The greater quantity of the water 

 in our bodies is derived from without, but it is probable that a small amount is 

 formed within our bodies by the action of free oxygen on certain organic sub- 

 stances. According to some observers, peroxide of hydrogen (B. 2 2 ) is also 

 present in the body.] 



II. Gases. [Oxygen is absorbed from the air, and enters the blood, where it 

 forms a loose chemical compound, with the colouring matter or haemoglobin, while 

 a small amount exists in a free state, or is simply absorbed.] Hydrogen is found 

 in the alimentary canal. Nitrogen [like oxygen, is absorbed from the atmosphere 

 by the blood, in which it is dissolved, and from which it passes into other fluids 

 of the body. It is probable that a very small quantity is formed within the body.] 



The presence of Marsh gas (CH 4 ) (p. 255), ammonia (NH 3 ), and sulphuretted 

 hydrogen (H 2 S) (p. 372) has been referred to already. 



III. Salts. Sodium chloride [is one of the most important inorganic 

 substances present in the body. It occurs in all the tissues and fluids 

 of the body, and it plays a most prominent part in connection with 

 the diffusion of fluids through membranes, and its presence is necessary 

 for the solution of the globulins (p. 502). In some cases it exists in 

 a state of combination with albuminous bodies, as in the blood-plasma. 

 Common salt is absolutely necessary for one's existence; if it be 

 withdrawn entirely, life soon comes to an end. About 15 grammes 

 are given off in twenty-four hours, the great part being excreted by 

 the urine. Boussingault showed that, the addition of a certain 

 amount of common salt to the daily food of cattle greatly improved 

 their condition.] 



Calcium phosphate [ (Ca 3 P 2 08) is the moat abundant salt in the body, ag it forms 

 more than one-half of our bonea, but it also occurs in dentine, enamel, and to a 



