SECTION III 



THE TISSUES 



FROM the protoplasm of the cells the various tissues of the 

 body bone, cartilage, muscle, c., are formed. The structure 

 of these must be studied practically; all that will be at- 

 tempted here is to indicate how they are formed from the 

 primitive cell. 



The human body is originally a single cell, and from this, 

 by division, a mass of simple cells is produced. In the 

 embryo, these cells get arranged in three layers an outer, 

 a middle, and an inner the epiblast, mesoblast, and hypo- 

 blast. 



(A) THE YEGETATIYE TISSUES 



The Vegetative Tissues are those which support, bind to- 

 gether, protect, and nourish the body. They may be divided 

 into the Epithelial Tissues, formed from the epiblast or hypo- 

 blast, and consisting of cells placed upon surfaces, and the 

 Connective Tissues developed from the mesoblast, and con- 

 sisting chiefly of formed material between cells. 



I. EPITHELIUM 



1. Squamous Epithelium 



(a) Simple Squamous Epithelium. This is seen lining the 

 air vesicles of the lungs. It consists of a single layer of flat, 

 scale-like cells, each with a central nucleus. The outlines 

 of these cells are made manifest by staining with nitrate 

 of silver, which blackens the cement substance between the 

 cells. 



(6) Stratified Squamous Epithelium (Fig. 4). The skin 

 and the lining membrane of the mouth and gullet are covered 

 by several layers of cells. The deeper cells divide, and as 

 the young ones get pushed upwards towards the surface, and 

 away from the nourishing fluids of the body, the chemical 



