152 ANSWERS TO PRACTICAL QUESTIONS 



of many muscles. These perform their functions through 

 the unconscious action of the brain and spinal cord. A 

 blow paralyzes the nervous system, the muscles at once 

 cease to act, and the body falls by its weight. 



27. What is the cause of the difference between light and 

 dark meat in a fowl? 



The amount of blood which circulates through differ- 

 ent parts of the body. The organs of a fowl which are 

 used the most become the darkest. 



79. i. If a hair be plucked out, will it grow again ? 



Yes. A new hair will always grow out so long as the 

 papilla at the bottom of the follicle remains uninjured. 



2. What causes the hair to " stand on end" when we are 

 frightened? 



(See Physiology, page 65.) 



" Many of the unstriated muscular fibres from the true 

 skin pass obliquely down from the surface of the dermis 

 to the under side of the slanting hair-follicles. The con- 

 traction of these fibres erects the hairs, and by drawing 

 the follicles to the surface and drawing in a little point 

 of the skin, produces that roughness of the integument 

 called "goose-skin," or Cutis Anserina. The standing 

 on end of the hair of the head, as the result of extreme 

 fright, may be partly due to the contraction of such 

 fibres, as well as to the action of the occipito-frontalis 

 muscle." CUTTER. 



3. Why is the skin roughened by riding in the cold? 



(See Physiology ', page 65 ; also Answer to Question 2.) 



