72 OF FORMED MATERIAL AND TISSUE. 



matter of whicli the cell wall or capsule is composed 

 was bioplasm long before any cell wall was to be dis- 

 covered. On the formation of a cell of epithelium see 

 § 117. 



108. Of formed material and tissue. — The material 

 called tissue, exhibiting a definite structui'e, is not 

 simply deposited, like a crystal, from a solution of 

 the same substance, as has been suggested by some 

 authorities, nor does it result from the "fibrillation,^^ 

 " vacuolation," or " stratificaUon'' of a previously 

 homogeneous fluid or viscid mass, or by the aggre- 

 gation and coalescence of little particles precipitated 

 from an albuminous fluid, but it is invariably formed 

 from living matter, as this ceases to manifest its vital 

 properties. Every particle of matter that is to be- 

 come tissue must first pass through the living state, 

 and the properties, characters, and composition of 

 the tissue will be determined partly by the internal 

 forces or poivers of the living matter acting upon the 

 elements of which it is composed, and partly by the 

 external conditions present at the tirae when these 

 pass from the living to the formed state. 



109. Varying characters of formed matter. — The 

 formed material or matter resulting from the death 

 of bioplasm or living matter under certain conditions 

 varies remarkably. It may be a fluid holding cer- 

 tain peculiar substances in solution, like bile, a viscid 

 matter like mucus, a perfectly transparent structure- 

 less membrane, or a material exhibiting a definite 

 structure. To the latter the term tissue is usually 

 applied. Tissue may consist of a scarcely visible 

 web of very delicate fibres, holding in its meshes a 

 perfectly transparent fluid containing but a trace of 

 solid matter. It may exhibit well-defined characters, 

 like cartilage, bone, etc., or it may manifest peculiar 

 and very remarkable properties like muscle and 

 nerve. 



110. matter essential to the elemental unit or cell. 



