WHAT MAKES MAN GO 55 



vital energy can be studied like other forms of 

 energy, but there is a specific work accomplished 

 by living protoplasm only. This being the situa- 

 tion it is pertinent to inquire into some of the de- 

 tails of food manufacture, definitely illustrating 

 this specific work. 



There is in every country, even in time of 

 famine, an abundance of the chemical molecules 

 necessary for the manufacture of food, if these 

 can be brought under the influence of living green 

 plants. Unless these chemical bodies are thus 

 treated, they cannot be used as a source of energy 

 for hving protoplasm. 



What is the plant's mechanism that plays such 

 an important role in the life of man? In figure 

 1 6 is shown a section of a plant leaf containing 

 cells, each with a cell wall, cytoplasm, and nucleus, 

 parts found in all typical cells (figures 4-8) ; but 

 in addition there are several distinct bodies in the 

 cytoplasm which botanists have named chloro- 

 plasts. These chloroplasts are usually bright 

 green in color due to the presence of a pigment 

 commonly known as chlorophyll. This pigment can 

 be dissolved, leaving the chloroplast unchanged 

 in form. They do not have any constant shape 

 or size when examined in different plants. Their 

 chemical composition is very complex, but similar 

 in all instances. 



It is not, however, in their shape and composi- 



