CHAPTEE XXVIII 



THE CHEMICAL COMPOSITION OF THE BODY 



THE elements found in the body are carbon, nitrogen, hydrogen, 

 oxygen, sulphur, phosphorus, fluorine, chlorine, iodine, silicon, sodium, 

 potassium, calcium, magnesium, lithium, iron, and occasionally traces 

 of manganese, copper, and lead. 



Of these, very few occur in the free state. Oxygen (to a small 

 extent) and nitrogen are found dissolved in the blood ; hydrogen is 

 formed by putrefaction in the alimentary canal. With some few 

 exceptions such as these, the elements enumerated above are found 

 combined with one another to form compounds. 



The compounds, or, as they are frequently termed in physiology, 

 the proximate principles, found in the body are divided into 



(1) Mineral or inorganic compounds. 



(2) Organic compounds, or compounds of carbon. 



The inorganic compounds present are water, various acids (such 

 as hydrochloric acid in the gastric juice), ammonia (as in the urine), 

 and numerous salts, such as calcium phosphate in bone, sodium chloride 

 in blood and urine, and many others. 



The organic compounds are more numerous ; they may be sub- 

 divided into 



(Proteins e.g., albumin, myosin, casein, gelatin, etc. 

 Nitrogenous -| Simpler nitrogenous bodies e.g., lecithin, urea, 

 [ creatine. 

 [Fats e.g., butter, fats of adipose tissue. 



Non nifrna-^nmiQ Carbohydrates e.g., sugar, starch. 

 Non-nitrogenous -> a- /* . .,.,. iJL*~ 



\ Simpler organic bodies e.g., cholesterin, lactic 



acid. 



The subdivision of the organic proximate principles into proteins, 

 fats, and carbohydrates forms the starting-point of chemical physiology. 



Carbohydrates. 



The Carbohydrates are found chiefly in vegetable tissues, and 

 many of them form important foods. Some carbohydrates are, how- 

 ever, found in or formed by the animal organism. The most important 



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