208 PEACTICAL PHYSIOLOGY 



Inorganic Salts. These consist of salts of the alkalies and alkaline 

 earths. The chief acid radicle present is phosphoric acid, and this 

 exists in several states (a) Inorganic phosphates, (b) phosphorus of 

 lecithin, (c) phosphorus of nuclein, (d) phosphorus of phospho-carnic 

 acid, (e) phosphorus of inosinic acid. (/) Besides these the watery 

 extract contains another phosphorus containing organic compound of 

 unknown composition. 



Phosphorus, therefore, seems to be a very important constituent of 

 muscle, and its form of combination changes after muscular work, the 

 organically combined phosphorus being split off as inorganic phosphates 

 which are then washed out of the muscle by the blood, and appear in 

 the urine. It is on this account that the phosphates in the urine are 

 increased after muscular work. 



EXPERIMENT IV. A watery extract of muscle has been freed of 

 proteids by boiling it. Add to the clear filtrate a few drops of 

 ammonia till faintly alkaline, and then a 10 per cent, solution of 

 calcium chloride. A white precipitate of phosphates results. 1 



CHAPTER X. 

 FOODS AND THE PRINCIPLES OF DIETETICS. 2 



IN the tissues, more especially in the muscles and glands, chemical 

 processes are constantly going on which lead to the production of 

 the energy thermic and mechanical necessary for life. These 

 chemical processes consist of the decomposition and oxidation of 

 complex molecules into simpler ones, during which a large amount 

 of potential energy, which had been stored up in the complex 

 molecules, is set free as actual or kinetic energy. The complex 

 substances necessary for this process are supplied by the food- 

 stuffs absorbed from the intestine. It is consequently necessary to 

 supply these bodies to the organism from without, and besides, to 

 supply water, which is required for the circulation of the blood and 

 lymph. 



The tissues themselves are also subjected to a considerable amount of 

 tear and wear, and the repair of this is effected by the proteids and 

 inorganic salts, and by these alone. 



1 That this precipitate consists of phosphates can be proved by dissolving in it 

 nitric acid and testing with molybdate of ammonia. 



2 The advanced chapter on this subject is under the heading of Metabolism. 



