CHAPTER I 



EXCHANGE OF MATERIAL 



SUMMARY. 1. Historical account of researches upon metabolism. 2. Methods 

 employed to determine the qualitative and quantitative data of the balance between 

 intake and output. 3. Two typical examples of balance of exchange of material 

 in man. 4. Difference in the resistance of man and animals to deprivation of 

 food. 5. Inanition and hibernation : relative and absolute loss of weight of the 

 different tissues during abstinence from food ; course of the curve of total loss 

 during the three phases of starvation. 6. Consumption of material during fasting 

 deduced from analyses of the urine and respiratory products ; influence of size of 

 body, age, sex, and constitution. 7. Exchange upon a diet of meat. 8. Exchange 

 on a diet of fats and carbohydrates with or without the addition of protein. 9. 

 Nutritive value of the digestive products of foods and gelatine. 10. Alcoholic 

 drinks, condiments, spices, and aromatic substances. 11. Water and the mineral 

 salts contained in the ashes of food-stuffs. 12. General conclusions and theory 

 of exchange of material. Bibliography. 



FROM our study of the physiology of the organs of vegetative and 

 animal life we see clearly that life without incessant consump- 

 tion and transformation of material and energy is inconceivable. 

 With the disintegration of extremely complex and unstable 

 molecules into simpler and more stable ones (exchange of material 

 or metabolism], there is, as a fundamental condition of life, a 

 transformation of potential into actual energy (exchange of 

 energy). 



Since the chemical metamorphoses of the animal organism 

 result in products which are richer in oxygen than the original 

 substances, it is obvious that these chemical changes consist 

 mainly of oxidation or slow combustion, either direct or indirect 

 processes due to special enzymes (oxidases) which are present 

 and are being formed continually in the living elements of the 

 tissues. 



The simplest products of the oxidising processes occurring in 

 the animal organism are water, carbon dioxide, sulphuric acid, 

 and phosphoric acid, in which the elements are combined fully 

 with oxygen. There are, however, many other end-products, 

 which from the chemical point of view represent products of 

 incomplete oxidation; these are represented by more complex 



VOL. v l B 



