PROTOPLASM 21 



in fats, the proportion of hydrogen and oxygen being the same as in 

 water, or two to one. Only two kinds can be shown to exist as such in 

 the tissues of the body, dextrose and glycogen. 



The water present in protoplasm maintains many substances in solu- 

 tion. Water, however, is important as a constituent of protoplasm, 

 not only as a very effective solvent but also because of its high specific 

 heat, because of its comparatively high surface tension, and because of 

 the fact that its presence gives to protoplasm the necessary consistency 

 and enables it to vary this consistency. The high specific heat of water 

 makes necessary the application of a large amount of heat to raise its 

 temperature and allows it to give off a correspondingly large amount of 

 heat in coohng, thus enabling it to exert a protective effect against sudden 

 and extreme temperature changes in the living body. 



Salts are present in considerable number and are to a large degree 

 ionized, though the degree varies with different salts. They aid in the 

 maintenance of certain other substances in solution and take part in some 

 of the reactions which are characteristic of Hving matter. Some of these 

 salts are the chlorides, phosphates, and carbonates. 



3. The various substances enumerated above are associated together 

 in a chemical aggregate or mixture which contains several thousands of 

 atoms combined into many kinds of molecules. Thus protoplasm is not 

 so simple as other famihar substances but represents a complex of sub- 

 stances all associated together in a certain definite fashion. 



This definite arrangement of substances in protoplasm may be termed 

 its chemical organization and is one of the most striking of its characters. 

 What this organization means may be illustrated in the following way: 

 One might go to a jewelry store and ask the jeweler to give him every part 

 which enters into the formation of a watch. The jeweler could place 

 in his hand the necessary number and kind of wheels, screws, pinions, 

 and jewels as well as the hands, dial, case, and so on, so that within his 

 hand he would hold everything necessary to make a complete watch. 

 He would not, however, have a watch. This assemblage of parts does not 

 become a watch capable of performing the service expected of it until 

 these parts have all been arranged in a certain very definite relation of one 

 to the other. So it is with the chemical substances which make up proto- 

 plasm. Without the necessary organization the assemblage of parts 

 named above is not a watch, and in the absence of the chemical organiza- 

 tion which is a property of protoplasm that substance cannot be said to 

 exist. This organization is made possible by the fact that protoplasm is a 

 colloidal emulsion and the various constituents may be distributed among 

 the droplets of the disperse phase and through the continuous phase. 



4. Protoplasm is very unstable. It alters in composition in response to 

 every change in the environment about it and when active remains for no 

 two consecutive moments the same. 



