INTRODUCTION 



Chemical physiology is mainly concerned with the materials of 

 which the tissues are composed and the results of the metabolic 

 changes which these materials and also ingested foodstuffs undergo. 

 As Haldane pointed out in his interesting book, Mechanism, Life and 

 Personality, " Biology deals at every point with phenomena which, 

 when we examine them, can be resolved into metabolic phenomena- 

 exchange of material and energy, as exemplified in growth, develop- 

 ment, maintenance, secretion and absorption, respiration, gross 

 movements in response to stimuli and other excitatory processes." 

 But to quote Haldane again : " We must not mistake measurements 

 of the balance of matter or energy entering and leaving the body, for 

 information as to the manner in which this stream passes through 

 the living tissues." 



Still a great deal of information is now available as regards the 

 ultimate fate and in part of the intermediate fate of specific sub- 

 stances ingested. Before however a proper appreciation of the 

 intricacies of the numerous metabolic phenomena, both of the 

 anabolic or synthetic type or of the catabolic or disintegrative 

 type can be obtained, it is necessary that the chemical properties 

 of the materials which compose the living tissue and the nature of 

 the various tissues themselves be studied. 



It is true but regrettable that many of the tests and reactions of 

 chemical physiology do not give the sharp end points and definite 

 results to which the student has become accustomed in ordinary 

 chemistry. This is largely due to the fact that the majority of the 

 materials which are dealt with belong to that highly complex series 

 of substances known as the colloids. Further, the student has to 

 grasp the fact that the mere elementary composition, i.e. the content 

 of the substance in Carbon, Hydrogen, Oxygen, Nitrogen, etc., 

 gives little or no information of value when applied to the colloidal 

 materials as found in the tissues where they rarely exis,t in a pure 

 state. Although the word protoplasm is often used as being almost 

 synonymous with protein, this is not the case. True, it is perhaps 

 probable that in the majority of instances protein is the predominant 

 substance in the protoplasmic mass of the cell, yet intimately 

 incorporated with the protein are found carbohydrates and fatty 

 substances. 



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