THE CELL. 39 



This process is carried forward under the influence of sunlight. 

 Thus the plant stores up the energy of the sunbeam in complex 

 molecules to be utilized by man and other animals. 



Other carbo-hydrates often occurring in a cell are dextrin, glu- 

 cose, cane sugar, etc. 



(3) Mineral salts. These often occur in a cell in crystalline 

 form. Crystals in plant cells are called raphides. 



(4) Proteids. These occur in plant cells as crystalloids and 

 aleurone grains. Crystalloids are protoplasmic bodies, crystalline in 

 form, but not in character. Aleurone grains are proteid granules 

 generally associated with crystalloids. 



(5) Fat occurs in the cell as globules. It contains the same ele- 

 ments as starch, but the hydrogen and oxygen are not in the pro- 

 portion of water. It serves as a reserve food supply. 



(6) The volatile oils, such as turpentine, bergamot, and asa- 

 fetida, occur especially in plant cells, and give to plants their per- 

 fumes. 



(7) The alkaloids are organic bases bearing nitrogen. The solid 

 alkaloids contain oxygen, whereas those that are liquid and volatile 

 do not. When reacting with acids they form soluble salts. They 

 furnish many powerful poisons and useful medicines, and are char- 

 acteristic of plants. 



(8) The ferments are nitrogenous compounds which have the 

 power to bring about important chemical changes in organic sub- 

 stances. 



KINDS OF CELLS. 



The important kinds of plant cells are parenchymatous and 

 prosenchymatous cells, traclieids, and vessels. Some of the varieties 

 of animal cells are leucocytes, epithelial cells, cartilage cells, bone 

 corpuscles, marrow cells, lymphoid cells, etc. 



FUNCTIONS OF CELLS. 



The cell is the laboratory of the body in which are manufactured 

 all those complex products which enter into its structure. The 

 processes by which these products are elaborated are andbolism 

 (building up) and Jcatabolism (breaking down). The two proc- 



