63 



LECTURE Y. 



Of Elementary Organs and Tissues — Of the Functions 

 of Organs and Tissues — Changes during Idfe — Of 

 the Elementary Units — Erronemis vieivs on Cell- 

 Formation— Formation of the Unit or Cell — Formed 

 Matter — Tilings essential to the Cell — Nutntion of 

 an Elementary Part — Of the increase of Cells — 

 Cuticle — Hair, Horn, Nail — Epithelial Textures 

 hardened with Calcareous Matter — Enamel — Een- 

 tine — Dentinal ^' tubes" — Of Secreting Cells — 

 Different Products formed hy the same Bioplasm — 

 Fat - Cell — Starch - Cell — Secondary Deposits — 

 Ciliated Cells — Pigment Cells — Salivary Corpuscles. 



98. Elementary organs and tissues. — The body of 

 tlie adult man or animal is made np of many different 

 organs, wliicli perform very different offices. These 

 all derive the elements of their nntrition from the 

 blood, and are all under the control of the nervous 

 system. The nervous system consists of many dif- 

 ferent parts, but these are all connected by inter- 

 communicating cords or nerve fibres. Each organ is 

 composed of a great nrunber of elementary organs 

 closely resembling one another, and so combined 

 that the work of all is united together. Every 

 elementary organ is made up of a variety of textures 

 differing from each other in appearance and struc- 

 ture, and in the offices they discharge. 



99. Tissues of a limb. — If a transverse section be 

 made, for example, of the fore leg of an animal, we 

 find externally a texture which is well known to all 

 as the skin — a tissue not simple in its structure, but 



