64 THE MECHANICAL FUNCTIONS. 



limpid, and none are perfectly simple in their 

 composition ; for they generally contain more or 

 less of a gelatinous matter, which, when very 

 abundant, imparts to them viscidity, constituting 

 an approach to the solid state. Many fluids con- 

 tain minute masses of matter, generally having 

 a globular shape, which can be seen only by 

 means of the microscope, and which float in 

 the surrounding liquid, and often thicken it in 

 a very sensible manner.* We next perceive 

 that these globules have, in many instances, 

 cohered, so as to form solid masses ; or have 

 united in lines, so as to constitute fibres. We 

 find these fibres collecting and adhering to- 

 gether in bundles ; or interwoven and aggluti- 

 nated, composing various other forms of texture ; 

 sometimes resembling a loose net-work of fila- 

 ments ; sometimes constituting laminae or plates ; 

 and, at other times, both plates and filaments 

 combining to form an irregular spongy fabric. 

 These various tissues, again, may themselves be 

 regarded as the constituent materials of which 

 the several organs of the body are constructed, 

 with different degrees of complication, according 

 to the respective functions which they are called 

 upon to perform. 



We shall now examine the several kinds of 



* Globules of this description have been found in the lymph, 

 the saliva, and even in the aqueous humor of the eye. 



