XIV. THE CHEMISTRY OF THE ANIMAL BODY. 



Introduction. Living matter contains hydrogen, oxygen, sulphur, chlo- 

 rine, fluorine, nitrogen, phosphorus, carbon, silicon, potassium, sodium, calcium, 

 magnesium, and iron. Abstraction of one of these elements means death to 

 the organization. The compounds occurring in living matter may for the 

 most part be isolated in the laboratory, but they do not then exhibit the prop- 

 erties of animate matter. In the living cell the smallest particles of matter 

 are arranged in such a manner that the phenomena of life are possible. Such 

 an arrangement of materials is called protoplasm, and anything which disturbs 

 this arrangement results in sickness or in death. Somatic death may result 

 from physical shock to the cell ; or it may be due to the inability of the cell or 

 the organism to remove from itself poisonous products which are retained in 

 the body so affecting the smallest particles that functional activity is impossible. 

 Pure chemistry adds much to our knowledge of physiology, but it must always 

 be remembered that the conditions present in the beaker glass are not the con- 

 ditions present in the living cell, physical and chemical results being dependent 

 on surrounding conditions ; hence the necessity and value of animal experimen- 

 tation. From chemical changes, the physical activities, i. e. the motions cha- 

 racteristic of life, result. Hence the chemistry of protoplasm is the corner-stone 

 of biology. The plan of this section is designed to consider the substances 

 -concerned in life in the order usually followed by chemical text-books. 



THE NON-METALLIC ELEMENTS. 

 HYDROGEN, H = l. 



This gas is found as a constant product of the putrefaction of animal 

 matter, and is therefore present in the intestinal tract. It is found in the 

 expired air of the rabbit and other herbivorous animals, and in traces in the ex- 

 pired air of carnivorous animals, having first been absorbed by the blood from 

 the intestinal tract. By far the greater amount of hydrogen in the animal 

 and vegetable worlds, as well as in the world at large, occurs combined in the 

 form of water, and it will be shown that the proteids, carbohydrates, and fats, 

 characteristic of the organism, all contain hydrogen originally derived from 

 water. In the atmosphere is found ammonia in traces, which holds hydrogen 

 in combination, and this is a second source of hydrogen, especially for the con- 

 struction of the proteid molecule. 



Preparation. (1) Through the electrolysis of water, by which one volume 



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