730 The Outline of Science 



As we have seen in a previous chapter, the energy transformer is 

 the green plant-cell aided by the green colouring matter, called 

 chlorophyll, which it contains. 



It is interesting to note that carbon exists on earth in differ- 

 ent forms ; there are three modifications of it to be found, all very 

 different in outward appearance, and it may be added, of different 

 values in human estimation. We have carbon in the black and 

 opaque form of charcoal, and as graphite or common black-lead, 

 and in the transparent crystalline form of a brilliant diamond. 

 All these things are merely different forms of the same "stuff." 

 And yet, although successful efforts have been made to manu- 

 facture artificial diamonds, it has not been found possible to do 

 so on a commercial basis, that is to say, it is still cheaper to pro- 

 cure them by expensive means from the natural resources than to 

 manufacture them in the laboratory. 



The Regulation of Vital Phenomena 



Sulphur in small quantity is an essential part of the 

 C-H-O-N-S compounds called proteins. Phosphorus is neces- 

 sary for the formation of chromatin, which is so important as a 

 vehicle of hereditary characters ; it is essential in the formation of 

 tissues so different as bone and brain. 



Potassium is the most active of metals biologically con- 

 sidered, and its salts play an important part in the regulation of 

 vital phenomena. Magnesium is an essential constituent of 

 chlorophyll, in the making of which iron is also necessary though 

 not included in its composition. Iron also occurs in the red 

 pigment of the blood which captures oxygen from the outer 

 world. Calcium compounds play an important part in stimu- 

 lating or slowing vital processes. So we might continue, but 

 we have said enough to suggest the manifold ways in which 

 the various qualities of elements are utilised in the service of 

 life. 



