316 THE WOKLD OF LIFE 



first is always present in cells, and consists of five elements — 

 carbon, hydrogen, sulphur, nitrogen, and oxygen. The two 

 other groups of organic bodies, carbohydrates and fats, con- 

 sist of three elements only — carbon, hydrogen, and oxygen, the 

 carbohydrates forming a large proportion of vegetable products, 

 the fats those of animals. These also are highly complex in 

 their chemical structure, but being products rather than the 

 essential substance of living things, they are more amenable 

 to chemical research, and large numbers of them, including 

 vegetable and animal acids, glycerin, grape sugar, indigo, 

 caifeine, and many others, have been produced in the labora- 

 tory, but always by the use of other organic products, not from 

 the simple elements used by nature. 



The atomic structure of the proteids is, however, so wonder- 

 fully complex as to be almost impossible of determination. 

 As examples of recent results, haemoglobin, the red colouring 

 matter of the blood, was found by Preyer in 1866 to be as 

 follows — 



^eoo-tlgeo-^ 154-'^ ^1^3^179? 



showing a total of 1894 atoms, while Zinoffsky in 1855 found 

 the same substance from horse's blood to be — 



C'7i2-tiii3o-'^ 214^245!' 6l^2> 



showing a total of 2301 atoms. Considering the very small 

 number of atoms in inorganic compounds, and in the simpler 

 vegetable and animal products, caffeine containing only 23 

 (C7H7(CH3)N402), the complexity of the proteids will be 

 more appreciated. 



Professor Max Verworu, from whose gTeat work on General 

 Physiology the preceding account is taken, is very strong in 

 his repudiation of the idea that there is such a thing as a 

 '' vital force." He maintains that all the powers of life reside 

 in the cell, and therefore in the protoplasm of which the cell 

 consists. But he recognises a great difference between the 



