202 THE SKIN 



through the translucent skin. It is greatly heightened 

 when the blood-vessels dilate in blushing, in exercise, 

 or as a reaction to the cold. A sudden pallor is due 

 to a contraction of the blood-vessels from cold or to 

 a lowering of the blood pressure associated with fear 

 or faintness. Persistent or chronic pallor is frequently 

 due to a chronic contraction of the blood-vessels in the 

 skin, or to a deficiency in. the red corpuscles of the 

 blood. The gaining of a good color, therefore, is often 

 dependent upon improving the health by fresh air and 

 exercise, which enrich the color of the blood itself. 



Dermis. Below the epidermis, we find the true skin, 

 the dermis, which is also -made up of numerous layers 

 of cells. The cells of the upper layers are compactly 

 joined together, whereas the deeper ones shade off into 

 soft fibres which blend with the underlying tissue. The 

 dermis is richly supplied with blood-vessels, and con- 

 tains the nerve terminals which receive the impressions 

 of touch. It also contains in part the ducts of the 

 sweat glands and the hair roots. 



Connective tissue layer. Underneath the dermis, 

 there is a less well-defined layer, consisting largely of 

 loose connective tissue, the spaces of which are more or 

 less filled Avith fat cells. This layer is of considerable 

 thickness in stout 'persons. It is made distinct from the 

 underlying muscles and other tissues by a loose mesh- 

 work of connective tissue, such as was found between 

 the large bundles of muscles. Its purpose is to permit 

 the skin to slip freely over the underlying parts, so that 

 it will not interfere with the contraction of the muscles 

 and the bending of the joints. The thickness of the skin 

 when picked up between the thumb and finger is mainly 

 due to this fatty layer, the other layers being com- 

 paratively thin. 



