THE CELL 



39 



hydrate. Other plastids are known to be the site of formation of fats 

 and others are known to be the origin of ferments, or enzymes 



(p. 78). 



Plants and Animals. Biology is a study of life processes 

 wherever they may take place. We are familiar with the fact that 

 two different types of life may be recognized, plant and animal. 

 The study of plants is called botany, the study of animals is called 



%f-i^ 



W^ -j^ 



J"-^-' 



If- .4. ^ ^'"^ _^ ^-^ ^ ^ . . ^ - r -. ■ ./ ■ .\ 



PLASTID 

 — VACUOLE 



■ cyro PLASM 



CENTROSPHERE 

 ■ CENTROSOME 



CHROMATIN 

 - NUCLEUS 



NUCLEAR MEMBRANE 

 — MITOCHONDRIA 



■PLASMA MEMBRANE 

 — CELL iVALL 







ANIMAL CELL 



PLANT CELL 



Fig. 8. — Diagrams to show certain structural similarities and differences between 

 animal and plant cells. It will be noted that the centrosphere and centrosomes are 

 absent from the plant cell and that plastids are more numerous and more con- 

 spicuous in the plant than in the animal cell. The wall of the plant cell is in 

 general thicker than that of the animal cell. 



ZOOLOGY. An organism may be studied in several ways; one may 

 concentrate on its anatomy, or structure, or on its functioning, or 

 PHYSIOLOGY. From what has gone before, we are now aware of the 

 fact that to comprehend the major principles of living the study of 

 structure and of function cannot be separated. So both Anatomy 

 and Physiology are incorporated into the study of Animal Biology. 

 But at once we are confronted with the questions : What constitutes 

 an animal .f* What distinguishes animals from plants .^^ Are the dif- 



