STUDY OF THE SKIN 171 



II. Describe the skin of the hand as it appears to the eye. Tiny structures 

 in the deeper layers of the skin push up the outer layer into little ridges. 



A. Note the arrangement of the lines on the tips of the fingers, particu- 

 larly the thumb. Describe the arrangement. 



B. Moisten the finger slightly and, if convenient, touch powdered car- 

 bon with it. Then press it on clean blank paper. 



1. What is the impression called? 



2. What use may finger prints serve? 



C. Examine your skin and observe whether it normally has breaks or 

 abrasions on it. What is the value of an unbroken skin ? 



III. Hold the hand out straight and then clinch the fist. Does the skin 

 appear dry and brittle or soft and flexible ? 



A. This characteristic is due to oil secreted in oil glands in the skin. 



B. Describe what may have happened to cause dry skin. 



IV. Touch your tongue to the back of your hand. Describe the taste. 

 This is due to perspiration secreted by sweat glands in the skin. 



A. Why is the perspiration not always seen on the skin ? 



B. What condition favors the evaporation of the perspiration ? 



C. What condition hinders the evaporation of the perspiration ? 



D. Under what conditions do we perspire excessively ? Why ? 



V. If wet-and-dry-bulb thermometers are available, pour a little water on 

 the bulb. 



A. After a few minutes, read and record the temperatiu-e of each 

 thermometer. 



B. What effect has the evaporation of moisture on temperature ? 



C. What effect would you expect the evaporation of perspiration to 

 have on the temperature of the body? 



VI. Hold the hand so that the back of it is on a level with the eyes. Note 

 the hairs covering it. These hairs probably help to absorb perspiration from 

 the skin. 



VII. Cite some evidences of the skin gradually peeling from your body. 

 This is the outer dead skin called the epidermis. 



VIII. Prick the skin gently with a pin. As a result of the pin prick tell : 



A. What two sensations may be experienced by the nerve endings in 

 the skin. 



B. What other sensation may be experienced by skin ? 



IX. Summarize your answers to the above questions by stating four 

 functions of skin. 



