24 CELLULAR TISSUES. 



The most simple or elementary texture of vege- 

 tation is a somewhat similar structure to that which 

 exists in animals. The first trace of the latter that 

 can be observed consists of a very soft and pulpy 

 cellular tissue, which, at this early period, is loaded 

 with fluid. In its nature, it is homogeneous, pre- 

 senting neither interstices nor fibres ; but it may 

 readily be permeated by air or liquids so as to pro- 

 duce small cells, and it may likewise be drawn out 

 into glutinous filaments. 



And how amazingly minute are these constituents ! 

 The white glistening threads traversing fibrous mem- 

 branes, may be discerned by the naked eye ; but so 

 far from being single, they are actually bundles of 

 fibres, requiring a microscopic power to distinguish 

 any one of them. It is probable that those forming 

 the cellular tissue are the most minute ; they are 

 said to vary from ^ to ^ of a line in diameter 

 a line being one-twelfth of an inch ; their edges 

 are quite smooth, they are transparent, and appear 

 to be composed of gelatine. Not only do they form 

 bundles, and thus constitute larger fibres, but ar- 

 ranged side by side they become the most delicate 

 membranes. 



In the species of animals placed at the bottom of 

 the scale, cellular tissue is generally believed to 

 constitute the entire body. In such instances, some 

 of which we shall hereafter consider, the body of 

 the animals consists of a soft gelatinous substance, 

 composed of translucent globules, which, however, 



