7JV HUMAN PHYSIOLOGY. 155 



winter-coat of an animal is warmer than its smooth sum- 

 mer-coat. 



13. Why do fowls shake out their feathers erect before 

 they perch for the night ? 



(See Question 12.) 



This is a wise provision of Nature to protect the fowl 

 against the chilliness of the night. More air is confined 

 by the roughened feathers, and thus the internal heat of 

 the bird is prevented from radiating. 



14. How can an extensive burn cause death by congestion 

 of the lungs ? 



The insensible perspiration is stopped upon the burned 

 surface, and the excretions are sent to the lungs, which 

 are overworked and overloaded by the excess. 



(See Physiology, page 74.) 



15. Why do we perspire so profusely after drinking cold 

 water ? 



The vital organs being chilled for an instant, the blood 

 is sent to the surface, a reaction is produced, the skin 

 acts more vigorously as an excretory organ, and the 

 insensible perspiration is thrown off more rapidly. 



1 6. What are the best means of preventing skin diseases, 

 colds, and rheumatism ? 



The skin should be kept in a healthy state by bathing, 

 rubbing, etc. Exposure to sudden changes of tempera- 

 ture should be avoided as far as possible. Flannel 



