98 STUDIES OF ANIMAL LIFE. 



rangement by a sketch of two adjacent barbs witli 

 their barbules. 



10. Find the small " hooks " on the barbules for hook- 



ing the barbs togetlier. (l.p.) 



11. Are the hooks on the distal or on the proximal 



barbules ? 

 Why is it necessary for the barbs to be hooked 



together ? 

 Why would not a solid, leaf -like feather answer as 



well? 



12. Have birds any other exoskeletal parts besides 



feathers ? 

 Why are feathers better than scales ? 



13. Draw a feather. 



E. Hair or Fur. 



1. What are the advantages of a hairy covering? 



2. Are there any hairs which have a sensory function ? 



3. How does the root differ from the shaft in color? 

 The part of a hair which is embedded in the skin is 



called the root and the remaining portion is the 

 shaft. 



4. In a prepared section of the scalp observe (l-p.), — 

 (a) the hair follicle, the pocket of the skin in which 



the root of the hair is embedded; 



(6) the papilla, the small knot of blood-vessels and 

 nerves in the enlarged base of the root; 



(c) the oil gland, lying beside the follicle and open- 

 ing into it; 



(c?) the hair muscle, which runs from the base of the 

 follicle diagonally to the surface of the scalp. 

 What is the use of this muscle ? 



5. Make a diagram to illustrate E 1. 



