18 PHYSIOLOGICAL CHEMISTRY 



tionship between chemical composition and biological function, 

 to be able to explain the workings of cells or of the various or- 

 gans and tissues in terms of chemical reactions, but experi- 

 menters are still far from the attainment of this end, although 

 many problems now are clearly understood which a few years 

 ago were still unsolved. The findings of physiological chem- 

 ists, and the methods of analysis developed by them have been 

 of the greatest value to the science of medicine in general, and 

 to the medical practitioner in particular. Since the body is 

 made up of chemical compounds, and since many of its activ- 

 ities depend upon chemical reactions, it is obvious that any 

 light thrown upon the nature and properties of its components 

 will tend to make clearer the character of the reactions in- 

 volved in the normal functioning of the tissues, thus furnishing 

 a basis for the study and correction of abnormal or diseased 

 conditions. Both diagnosis and treatment have come to depend 

 more and more upon the findings of the physiological chem- 

 ists, and the general advancement of medicine has been greatly 

 furthered by the results of biochemical research. 



Protoplasm. Living material, whether of plant or animal 

 origin has been found to consist of a substance which is strik- 

 ingly uniform throughout the entire living world. This ma- 

 terial has been given the name protoplasm (from the Greek 

 words meaning "first," and "form"). It is a jelly-like 

 watery mass, sometimes fairly rigid in form, possessing cer- 

 tain characteristics which serve to distinguish living from life- 

 less material. The first of these is the power of growth, 

 growth from internal forces such as we observe in animals and 

 plants, and not growth from without such as the enlarging of 

 a crystal. The second is the power of respiration, taking up 

 oxygen and giving off carbon dioxide. The third is the power 

 of movement, from place to place in animals, and movement 

 incident to growth in plants. The fourth is irritability, and the 

 fifth the power of reproduction. All living material possesses 

 these five properties, and no lifeless material possesses all of 

 them. Physiological chemistry may be looked upon as the 



