EXCRETION 



95 



Pick up a little of the skin between the fingers. Is it at- 

 tached to the underlying muscles? About how thick is it 

 on the back of the hand? on the base of the thumb? 



Sweat-Duct 



Sebaceous Gland 



Horny layer 

 Pigment layer 



Tactile Organ 



Nerve- 

 Blood Vessels 



Sweat Oland--^- 



Fat 



Epidermis 



Dermis 



FIG. 45. Diagram of Skin Section. 



B. Microscopic Study of a Section. Study the prepared 

 slide, under the high power. Note the layer character of 

 the epidermis, the papillae with their blood vessels, the coiled 

 sweat glands and their ducts (thick sections show these best) . 

 Sketch and label all parts of your drawing as in the dia- 

 gram. 



Compare the action of the sweat glands with that of the 

 tubuli uriniferse (uriniferous tubules) of the cortex of the 

 kidneys. When do we perspire most? Why does exercise 

 increase the amount? What is one function of the 

 skin? 



C. Study of Skin Modifications, (a) Hairs. Note the 



