LIFE AND PROTOPLASM , ,, 



hydrate, such as ghicose, for example, the chemist writes a fornuihi 

 representing a molecule of the substance. In such a simple nujlecule 

 the atoms of hydrogen and oxygen are usually united in the same 

 proportion as in water and the empirical formula is written CcHi-Oa. 

 This water proportion (H,.0) is maintained in other more complex 

 carbohydrates such as starch, but here the chemist writes an x after 

 the empirical formula (CeHioOa)^. This means that the molecular 

 formula is not exactly known but in the case of starch the x should 

 probably be about 200, which makes the molecule very much larger 

 than that of the simple sugar. The simple sugars with their small 

 molecules are ea.sily soluble in water, while the complex molecule of 

 the starch is not .so soluble. In fatty substances, oxygen is present in 

 a much smaller proportion than in the carbohydrates. An example 

 might be oleic acid, one of the components of butter fat, (Ci8H,3402). 

 Proteins have still more complex molecules. In the first place tliey 

 are built up of simpler substances, called amino acids, and in some 

 cases other radicals are added to them. For example, in the cell 

 nuclei the protein is combined with nucleic acid, which has the aston- 

 ishingly complex formula C38H49029Xi5P4, which really means very 

 little except to the student of chemistry. 



Protoplasm a Complex Mixture 



Living stuff, having the same elements as the complex foodstuffs 

 for a ba.sis, is even more intricate. No chemical compounds in nature 

 are quite as complicated in composition, for protoplasm not only 

 is made up of the foodstuffs but it also consists largely of water. 

 One estimate by weight gives 80 per cent water, 15 per cent proteins, 

 3 per cent fats, 1 per cent carbohydrates and other organic substances, 

 and 1 per cent inorganic salts. It has been determined that carbon, 

 nitrogen, hydrogen, oxygen, and phosphorus are alwaj's present in 

 protoplasm and are called the primary elements. Magnesium, pota.^- 

 sium, iron, and sulphur appear equally nece.s.sary for life. Sodium 

 and chlorine are always found in animal but only infrequently in jilant 

 tissues, and calcium appears necessary for life in the higher forms. 

 Other elements, bromine, fluorine, iodine, silicon, boron, manganese, 

 and even copper, zinc, and aluminum, are found in some organisms. 



While some of these elements are solids and others gases, none of 

 them, except oxygen, typically occurs to any marked extent free 

 in the organism. Nor are th(>y found free in the foods or waste 

 products, but rather as various kinds of chemical compounds which 



