CHAPTER II. 



CHEMIC COMPOSITION OF THE HUMAN BODY. 



Since it has been demonstrated that every exhibition of functional 

 activity is associated with changes of structure, it has been apparent that a 

 knowledge of the chemic composition of the body, not only when in a state 

 of rest, but to a far greater degree when in a state of activity, is necessary to 

 a correct understanding of the intimate nature of physiologic processes. 

 Though the analysis of the dead body is comparatively easy, the determina- 

 tion of the successive changes in composition of the living body is attended 

 with many difficulties. The living material, the bioplasm, is not only 

 complex and unstable in composition, but extremely sensitive to all physical 

 and chemic influences. The methods, therefore, which are employed for 

 analysis destroy its composition and vitality, and the products which are 

 obtained are peculiar to dead rather than to living material. 



Chemic analysis, therefore, may be directed 



1. To the determination of the composition of the dead body. 



2. To the determination of the successive changes in composition which 

 the living bioplasm undergoes during functional activity. 



A chemic analysis of the dead body, with a view to disclosing the sub- 

 stances of which it is composed, their properties, their intimate structure, 

 their relationship to one another, constitutes what might be termed chemic 

 anatomy. An investigation of the living material and of the successive 

 changes it undergoes in the performance of its functions constitutes what 

 has been termed chemic physiology or physiologic chemistry. 



By chemic analysis the animal body can be reduced to a number of 

 liquid and solid compounds which belong to both the inorganic and organic 

 worlds. These compounds, resulting from a proximate analysis, have 

 been termed proximate principles. That they may merit this term, how- 

 ever, they must be obtained in the form under which they exist in the living 

 condition. The organic compounds consist of representatives of the carbo- 

 hydrate, fatty, and protein groups of organic bodies; the inorganic compounds 

 consist of water, various acids, and inorganic salts. 



The compounds or proximate principles thus obtained can be further 

 resolved by an ultimate analysis into a small number of chemic elements 

 which are identical with elements found in many other organic as well as 

 inorganic compounds. The different chemic elements which are thus 

 obtained, and the percentages in which they exist in the body, are as follows 

 viz., oxygen, 72 per cent.; hydrogen, 9.10; nitrogen, 2.5; carbon, 13.50; 

 phosphorus, 1.15; calcium, 1.30; sulphur, 0.147; sodium, o.io; potassium, 

 0.026; chlorin, 0.085; fluorin, iron, silicon, magnesium, in small and variable 

 amounts. 



