HOUSING-SKIN AND ITS DERIVATIVES 373 



tough connective tissue (Fig. 14-1). The under the influence of the autonomic nerv- 

 nature of this layer becomes apparent if one ous system and may be influenced in some 

 recalls the various kinds of leather that are people by emotions such as in blushing 

 employed by man for thousands of pur- (vasodilation). Also, the dermis contains 

 poses. It is interesting to note that man uses many nerve endings which are receptors for 

 the skins of other animals to supplement his heat, cold, pressure, touch, and pain. With 

 own. Fat has a tendency to store itself in the exception of the pain nerve endings, 

 the deeper parts of the dermis and becomes they are specially designed end organs for 

 localized in characteristic regions of the special stimuli. Since the skin is in contact 

 body familiar to everyone. In unusual with the outer world all of the time, a great 

 cases, the stored fat can weigh as much as deal of information comes to the brain from 

 the remainder of tlie body, a character it. Pain, for example, is a very uncomfortable 

 which is admired by some races of people sensation, ideally designed to make the ani- 

 and abhorred by others. The disti-ibution mal do something about the situation, if 

 of this layer of fat is characteristic of the possible. This sensation is responsible for 

 sex. For example, in the female the layer is preservation of the individual, for without 

 thicker, giving the skin a more velvety it great areas of the body might be de- 

 touch and, the body contours are smoother stroyed without the organism being aware 

 curves with the underlying muscles less of it. A few people have no nerve endings 

 pronounced than is the case in males, in their skin and hence feel no pain; as a 

 Women are therefore better insulated than consequence, they can be seriously burned 

 men, although they seem to suffer more or injured in other ways before becoming 

 from the cold, perhaps due to their scanty conscious of the danger, 

 artificial covering, a mere fraction of that 



with which the male burdens himself. Thus we see that most animals possess 



Many tiny bundles of blood vessels pro- some sort of protective covering. They also 



ject up from below into the dermis where need some internal support, particularly the 



they function in bringing the blood close to larger forms and those animals tliat live on 



the surface for cooling the body when it is land. Let us study the way vertebrates, and 



too warm. They contract when the body is man in particular, have solved this prob- 



cold (vasoconstriction), preventing the lem. 

 blood from coming to the surface. They are 



