S2 THE MECHANICAL FUNCTIONS. 



nected together by fibres, and by other plates which cross 

 25 them in different directionSjleaving cavities or 



cells. (Fig. 25.) These cells, or rather inter- 

 vening spaces, communicate freely with one 

 another; and, in fact, may be considered as 

 one common cavity, subdivided by an infinite 

 number of partitions into minute compart- 

 ments. Hence the cellular texture is through- 

 out readily permeable to fluids of all kinds, and retains these 

 fluids in the manner, and on the same principle, as a sponge. 

 The cellular texture is not only the element, or essential 

 material employed by nature in the construction of all the 

 parts of the animal fabric; but, in its simplest form, it con- 

 stitutes the general medium of connexion between adjacent 

 oro-ans, and also between the several parts of the same organ. 

 Like the mortar which unites the stones of a building, the 

 cellular texture is the universal cement employed to bind 

 together all the solid structures. Its properties are ad- 

 mirably adapted to the mechanical purposes which are re- 

 quired in difierent parts of the frame: and these properties 

 are variously modified and adjusted to suit the particular 

 exigencies of the case. When, for instance, difierent parts 

 require to be moveable upon each other, the cellular sub- 

 stance interposed between them has its state of condensation 

 adapted to the degree of motion required. That which con- 

 nects the muscles, or surrounds the joints, and all other parts 

 concerned in extensive action, has a looser texture, being 

 formed of broad and extensible plates, with few lateral ad- 

 hesions, and leaving large interstices; while the more quies- 

 cent organs, the plates of the cellular substance, are thin and 

 small, the fibres short and slender, and their intertexture 

 closer and more condensed. 



Besides being flexible and extensible, the cellular texture 

 is also highly elastic, a property which is exceedingly advan- 

 tageous in the construction of the frame. Not only the dis- 

 placement of parts is resisted by their elasticity, but, when 

 displaced, they tend to return to their natural position. This 

 property performs a more important part in the mechanism 



