vented from doing its proper work 

 other organs try to carry it on, and the 

 result is that those organs which are 

 really beyond our control, and which 

 will work properly without any atten- 

 tion from us, become diseased by our 

 bad treatment of the organ that comes 

 first in the natural order of attention. 



The skin throws off waste matter 

 from the system. Two and one-half 

 pounds of watery vapor is poured out 

 daily from the average man. A clogged 

 skin retains certain salts in the system 

 supposed to have something to do with 

 such diseases as rheumatism and gout 

 if left in the blood by two little exer- 

 cise of perspiration. 



Besides the sweat glands there are 

 glands which exude fatty substances 

 upon the skin, keeping it suitably lubri- 

 cated and somewhat impervious to water. 

 In some animals this secretion is so abun- 

 dant that the skin cannot become wet 

 in swimming. Beneath the skin are 

 frequently cushions of fat to protect the 

 soles of the feet and the outside of the 

 larger joints. The blubber of the whale, 

 the thickest skinned of all animals, is of 

 this sort, and is evidently intended to 

 make his tremendous weight less de- 

 structive when brought in contact with 

 other objects. The hide of the swifter 

 ones is peculiarly fitted with large pa- 

 pillae of feeling which are supposed to 

 warn them of the presence of rocks and 

 other objects by the action of the water 

 while swimming near them. 



Insects, not having lungs, receive air 

 into their bodies through holes in the 

 skin. These are called spiracles. They 

 are so protected by hairs within the 

 holes that water will not enter them. 

 This is why it is so difificult to drown 

 an insect. But if you touch the abdo- 

 men of one of these skin-breathing 

 creatures, for instance the yellow part 

 of a wasp, with a drop of oil, the 

 minute openings become almost imme- 

 diately clogged and the insect falls 

 dead as if choked completely. 



The skin consists of two layers, both 

 of which are exceedingly interesting. 

 The outer or scarf skin is called the 

 cuticle on the outside of the body, 

 while wherever the skin dips into the 

 body it is modified into what is called 

 mucous membrane. This outer skin is 



not what is rubbed off the surface in a 

 Turkish bath manipulation or what is 

 brought off by the rubbing one gives 

 the body with a rough towel. These 

 rubbings bring off merely the dead 

 outer surface of the cuticle which 

 should be out of the way because no 

 longer useful. In man it continually 

 wears off, in serpents it is shed annually 

 in one slough. 



The cuticle is the portion of the cov- 

 ering of the body which may best be 

 noticed when a blister has been raised 

 in the skin. The blister is an accumula- 

 tion of fluid between the cuticle and 

 the true skin. 



The cuticle, or epidermis, is modified 

 in many other ways than the one in 

 which it becomes mucous membrane. 

 Where the habits of the animal make 

 warmth desirable the epidermis dips 

 into the skin and without any break in 

 its connection rises in the form of 

 wool, which covers the body of the 

 sheep so effectually. Where the ani- 

 mal is designed for flight there is the 

 same characteristic dip into the ma- 

 terial of the body, and out of the little 

 sac so formed rises the feather which 

 gives the bird its beauty and powers of 

 flight. The feather is a modification of 

 the scarf skin. 



Where protection is needed for the 

 body beneath the surface of the water 

 this changeable substance covers the 

 true skin with hard scales that make 

 the friction of the water as slight as 

 possible, while giving a firm and light 

 resisting surface to prevent wounds. 

 Horns and hoofs are modifications of 

 the scarf skin. Where claws or talons 

 are needed in the business of fighting 

 or tearing food in bits or digging holes 

 in the ground or elsewhere, the scarf 

 skin changes itself at the extremities 

 of paws and feet and produces nails, 

 talons, and claws, whose powers are 

 both marvelous and varied. For the 

 protection of most mammals the whole 

 of the body is favored by this power of 

 the scarf skin to produce whatever 

 seems necessary for the comfort of the 

 indi\'idual, and the body is indented 

 with innumerable minute holes called 

 hair follicles into which the scarf skin 

 dips and rises agiin to the surface 

 transformed into hairs of varying de- 



138 



