86 THE MECHANICAL FUiNCTlONS. 



tendons, and the cellular texture : for the most 

 recent, and apparently most accurate microscopical 

 observations tend to show that no globular structure 

 exists in any of these textures.* 



The element which we can recognise without 

 difficulty as composing the greater portion of 

 animal structures, is that which is known by the 

 name of the cellular texture. Although bearing 

 the same designation as the elementary material of 

 the vegetable fabric, it differs widely from it in its 

 structure and mechanical properties. It is not, 

 like that of plants, composed of a union of vesicles; 

 but is formed of a congeries of extremely thin 

 laminae, or plates, variously connected together by 

 23 fibres, and by other plates, which cross 



them in different directions, leaving 

 cavities or cells. (Fig. 25). These cells, 

 or rather intervening spaces, communi- 

 cate freely with one another; and, in 

 fact, may be considered as one common 

 cavity, subdivided by an infinite num- 

 ber of partitions into minute compartments. Hence 

 the cellular texture is throughout readily permeable 

 to fluids of all kinds, and retains these fluids in 

 the manner, and on the same principle, as a 

 sponge. 



* See the Appendix to Dr. Hodgkin and Dr. Fisher's translation 

 of Edwards's work on the Influence of Physical Agents on Life, 

 p. 440. 



The theory of Schleiden respecting the origin of vegetable cells 

 from a vesicular developement of nuclei, has been found by Schwann 

 to extend to animal structures also ; and a remarkable similarity is 

 traced by him in the phenomena of the early developement of both 

 these classes of organized beings. The conclusion which he deduces 

 from his microscopical investigations is, that all the animal tissues, 



