CHAPTER II 

 CELLS AND TISSUES 



36. The Place of Physiology among the Natural Sciences. 

 Natural objects have long been divided for purposes of 

 study into the Mineral, Vegetable, and Animal kingdoms. 

 Are any two of these divisions more closely related to 

 each other than they are to the third ? Yes, we find that 

 an animal and a plant resemble each other and differ from 

 a mineral in that they are both alive. In order to carry on 

 the mysterious process called life, animals and plants must 

 have an orderly growth and activity. The parts by means 

 of which they carry on this activity are called organs ; 

 and plants and animals together form what is called the or- 

 ganic kingdom, while minerals form the inorganic kingdom. 



37. The science which treats of living things in general 

 is called Biology. Botany is one of the biological sciences 

 and treats of plants. Zoology is another branch of biol- 

 ogy and treats of animals. 



38. We may study the body of an animal in two ways. 

 We may study the structure and forms of its organs ; this 

 science is called Anatomy, and it may be studied in the 

 dead body better than in the living animal. Or we may 

 study the actions or the functions of the organs of the living 

 animal; this science is called Physiology. It is divided 

 into Plant Physiology and Animal Physiology. Anatomy 

 is likewise divided into two sciences. 



39. The Study of the Human Body. The study you 

 have undertaken is generally, for convenience, called 

 Physiology ; but Anatomy must also form a part of the study, 



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