3 o 



Physiology. 



HAIR 



Experiment to show insensible Perspiration. Thrust the hand into 

 a cold glass jar. Note the moisture that soon gathers on the inside of 

 the jar from the insensible sweat of the hand. A common fruit jar will 

 do for a small hand, but a candy jar is better, having a larger mouth and 

 clear glass. 



The Structure of the Skin. The skin has two layers, 

 the inner, or dermis, and the outer, or epidermis. The 



epidermis is thick 



sweat Pore over the palms and 



soles; elsewhere it 

 is thin. The skin is 

 much thicker than 

 we would naturally 

 suppose, and makes 

 one fifteenth of the 

 weight of the body. 



The Epidermis. 



The epidermis con- 

 Cells sists of many layers 

 of cells packed 

 closely together. 

 The deepest cells 

 may be compared to 

 grapes with their cell 

 walls plumply filled out with the liquids of the cell. Sup- 

 pose for the inner' layer, grapes set on end, and so closely 

 packed together as to press each other more or less flat on 

 the sides. Above these are cells less closely pressed, more 

 nearly spherical ; then cells with less liquid in them, and 

 somewhat shrunken, like raisins. Then still dryer cells 

 flattened parallel with the surface of the skin. And, last, 

 in the outer part, layers of cell walls, dry and empty, pressed 

 flat like empty grape skins. These flat cell walls come off 



Hai 



Blood 

 Tube 



Fig. 64. Vertical Section of the Skin. 



