276 EXPERIMENTAL GENERAL SCIENCE 



the tissues beneath by an extra pad of its substance. When 

 we make a blister, it is the epidermis which is pushed out by 

 the accumulation of lymph beneath it. The deeper parts of 

 the epidermis contain varying amounts of pigment whose 

 relative abundance makes the difference between blondes and 

 brunettes. Exposure to the sun or wind causes more of the 

 pigment to develop. If this is spread in an even layer we call 

 it tan; if it occurs in spots it forms freckles. The negro's 

 skin is dark because of a superabundance of this pigment. 

 Occasionally an individual is found who entirely lacks pigment. 

 Such a person is called an albino. 



236. The Dennis. The dermis or true skin is made up of 

 connective tissue and is richly supplied with blood vessels and 

 nerves. It is loosely connected to the muscles beneath and 

 moves smoothly over them. It is this tissue in animals that 

 is tanned to make leather. At the point where the dermis 

 is in contact with the epidermis, that is, on its outer surface, 

 it is thrown up into small projections called papilla. Warts 

 are merely overgrown papillae. The papillae are set very 

 regularly on the palms of the hands and the finger tips and 

 this produces the fine lines or ridges with which everybody 

 is familiar. The lower layers of the dermis are often used by 

 the body for the storage of fat. This is especially noticeable 

 in the region over the abdomen. 



237. Outgrowths of the Skin. With the exception of the 

 palms of the hands and the soles of the feet, the skin is covered 

 with fine hairs. These hairs are each set in a depression of the 

 dermis and are supplied with blood vessels, nerves, and muscles. 

 Hairs are really tubes of the same tissue that forms the epi- 

 dermis. They grow from small elevations called hair follicles. 

 If a hair be pulled out, another will grow in its stead provided 

 the follicle is not injured. The hair, itself, contains neither 

 nerves nor blood vessels though these occur in the follicles. 

 When the skin is chilled, the muscles at the base of the hairs 



