ELEMENTARY STRUCTURE OF ORGANIZED BODIES. 13 



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 property. It ex- 

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

 in the most solid wood, 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 



/ V A / tissue of the house-leek (Fig. 1). The 



in, ^ ^v_y ' 



Fig. i. intervals which sometimes separate them 



from each other, are called intercellular passages or spaces 

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

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



* 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., all of which are indispen- 

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

 the discovery of the identity of the structure of animal and vegetable tis- 

 sues, a common denomination for this uniformity of texture, has been 

 justly preferred ; and the existence of tissues is now regarded as the basis 

 of organization. 



2 



