A MANUAL OF VETERINARY PHYSIOLOGY. 



CHAPTER I. 



THE CHEMICAL CONSTITUENTS OF THE ORGANISM. 



Chemistry shows that a large number of the so-called 

 elements enter into the composition of the body. Oxygen, 

 hydrogen, carbon, nitrogen, sulphur, phosphorus, chlorine, 

 fluorine, silicon, potassium, sodium, calcium, magnesium, 

 and iron are found, not in a free state, or only to a very 

 slight extent, but brought together in such a way as to 

 form compounds, and these may be divided into two classes 

 — Organic and Inorganic. 



Before reviewing the compounds of the body, we may 

 briefly notice the part played in nature by the various 

 elements, and the methods by which these enter the bodies 

 of animals ; this is especially interesting to the veterinary 

 physiologist, as, with few exceptions, the animals with which 

 he has to deal, and of which this book mainly treats, obtain 

 their store of the needful elements direct from the vege- 

 table kingdom, instead of through the intermediate stage of 

 the animal kingdom.* 



Carbon exists in nature principally in the form of carbonic 

 acid, viz., united to oxygen ; it is only in this compound 

 that it can be taken up by plants, which in their special 

 laboratory split off the oxygen molecule and store up the 



* Bunge, ' Physiological and Pathological Chemistry,' has been fol- 

 lowed in this account of the elements of the body. 



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