ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 37 



trates 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 to liquids. There 

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

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

 ists 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 or- 

 ganism is now applied. Hence the collective name of 

 organized beings,* which includes both the animal and the 

 vegetable kingdoms. 



37. The vegetable tissues and most of the organic struc- 

 tures, 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 Fig. 1. 



from each other are called intercellular passages or spaces 

 (m.) When the cellules are very numerous, and crowd 

 each other, their outlines become angular, and the intercel- 

 lular spaces disappear, as seen in figure 2, which represents 



* 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 

 have leaves, petals, stamens, pistils, roots, &c., which are indispensable 

 to the maintenance of life and the perpetuation of the species. Since 

 the discovery of the fundamental identity of structure of animal and 

 vegetable tissues, a common denomination for this uniformity of texture 

 haa been justly preferred ; and the existence of tissues is now regarded 

 as the basis of organization. 



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