10 ELEMENTARY. STRUCTURE OF ORGANIZED BODIES. 



be supplied, and they die, after having lived their appointed 

 period. Inorganic bodies, on the contrary, contain within 

 themselves no principle of destruction ; and unless subjected 

 to some foreign influence, would never change. The lime- 

 stone and granite of our mountains remain just as they were 

 formed in ancient geological epochs ; while numberless gene- 

 rations of plants and animals have lived and perished upon 

 their surface. 



SECTION II. 



ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 



35. THE exercise of the functions of life, which is the es- 

 sential characteristic of organized bodies ( 32), requires a 

 degree of flexibility of the organs. This is secured by means 

 of a certain quantity of watery fluid, which penetrates all 

 parts of the body, and forms one of its principal constituents. 



36. All living bodies, without exception, are made up of 

 tissues so constructed as to be permeable by liquids. There 

 is no part of the body, no organ, however hard and compact 

 it may appear, which has not this peculiar structure. It 

 exists in the bones of animals, as well as in their flesh and fat ; 

 in the wood, however solid, as well as in the bark and flowers 

 of plants. It is to this general structure that the term organism 

 is now applied. Hence the collective name of organized 

 which includes both the animal and the vegetable 



kingdoms. 



37. The vegetable tissues, and most organic structures, 

 when examined by the microscope, in their 

 early states of growth, are found to be 

 composed of hollow vesicles or cells. The 

 natural form of the cells is that of a sphere 

 or of an ellipsoid, as may be easily seen 

 in many plants ; for example, in the tissue 

 of the house-leek (Fig. 1). The intervals 

 which sometimes separate them from each 

 other are called intercellular spaces (wi)- 

 F- ^~~ When the cellules are very numerous, and 



* Formerly, animals and plants were said to be organized because they 

 are furnished with definite parts, called organs, which execute particular 

 functions. Thus, animals have a stomach, a heart, lungs, &c. ; plants 



