A YEAE IN SCIENCE 125 



structure? The inner layer is the derm-is. How does 

 it compare with the epidermis in thickness? Note 

 that its surface is ridged. These ridges are made up 

 of a number of papillae. Each papilla marks- the end 

 of a nerve of touch. Is the skin sensitive to other 

 stimuli than touch? If so, what are they? In the 

 dermis locate the fat cells, the roots of the hair, the 

 oil or sebaceous glands, and the sic eat glands. Where 

 do the ducts from the sweat glands open ? What effect 

 does the evaporation of sweat from the surface of the 

 skin have on the temperature of the skin? To answer 

 this question refer to Exercise 21. 



Make a drawing to show the parts of the skin. 



From this exercise what are some of the functions 

 of the skin? 



Hair and nails are modifications of the skin. 



CHAPTER XXII 

 SKELETAL SYSTEM 



Exercise 84. The Skeleton. 



Object: To study the general plan of the skeleton. 



Apparatus 



Skeleton 



Directions: The skeleton may be divided into three 

 parts : the head, trunk, and limbs with the bones to 

 which they are attached, hip and shoulder. 



A. Head. Notice that the head is divided into the 



