THE SKIN 



IS!) 



Figure 202. 



- Involuntary Muscle 

 Cells. 



The muscular tissue of the heart has characteristics of 

 both the voluntary and involuntary muscles, so that it 

 may almost be said to 



belong in a special class. 

 155. Skin. — The skin 

 covers and protects the 

 voluntary muscles, regu- 

 lates the body tempera- 

 ture, gives off waste matter, and acts as a general sense 



organ. The outer layer of 

 skin is called the epidermis, 

 and is chiefly composed of 

 dead cells. These outer cells 

 are constantly breaking off, a 

 process which is most apparent 

 in the case of sunburn. What- 

 ever pigment, or coloring mat- 

 ter, there is in our skin is located in the inner cells of 



Figure 203. — Heart Muscle 

 Cells. 



$BS! 



,-. - - 



Milk . 



Figure 204. — Various Forms of Cells in Human Body. 



a. side and top view of flat epithelium : b, c, columnar epithelium 

 d, e, ciliated epithelium. How do these cells differ from the muscle 

 cells in Figures 201-203? 



