STRUCTURE OP THE HUMAN BODY. 25 



Constitute the blood, or having performed some special office, 

 is moistening the various surfaces, are returned to the blood ; 

 icnce according to their nature, they are called aqueous, 

 ilbuminous, mucous, serous, &c. 



4. The solids are composed of the same chemical prin- 

 ;iples as the fluids, and by analysis are reduced to the same 

 iltimate elements. In the formation of solids, the particles 

 if matter are supposed to be arranged in one of two modes, 

 r iz., either in the form of minute threads or fibres, or of thin 

 dates or laminae ; hence every solid of the body is said to 

 v fibrous, or laminated. These fibres, or laminae are vari- 

 ously interwoven, and interlaced, so as to form a net-work ; 

 tnd the spaces included between them are called areolae, or 

 ells. According to some microscopical observers, the ulti- 

 mate animal solid is a minute sphere or globule of matter, 

 lot exceeding an eighth thousandth part of an inch in diam- 

 iter, 



5. The fibrous or laminated matter is often so arranged 

 s to form a structure, possessing distinct and peculiar 

 Toperties ; and each of these modifications is considered a 

 eparate form of organized matter, and is called a primary 

 Issue. These tissues have been variously classified by dif- 

 srent anatomists and physiologists, some making them to 

 onsist of five, viz., the membranous, the cartilaginous, the 

 sseous, the muscular, and the nervous; while others make 

 ut three, the cellular, the muscular, and the nervous. An- 

 ther arrangement is into filaments, fibres, tissues, organs, 

 pparatuses, and systems. 



6. A filament is made up of a series of minute or primi- 

 ive molecules, arranged in a row. A fibre is composed of 

 everal of these filaments united together, as the muscular 

 nd nervous fibres. A tissue is supposed to be composed of 

 bres disposed in planes, forming in this manner an expan- 

 ion, or when crossing each other, forming spongy solids, 

 rith cells interspersed throughout. In this" way are the 

 ellular, serous, and mucous membranes formed. When 



3 



