i68 PHYSIOLOGY FOR BEGINNERS CHAP. 



cells. The deepest layer consists of elongated or columnar 

 cells, lying perpendicularly side by side. The layers imme- 

 diately over this consist of cells which are shorter and many- 

 sided or round in shape. The cells over these gradually 

 become flatter and flatter till those of the surface layers are 

 reduced to mere thin scales. In the deeper parts of the epi- 

 dermis the cells are soft and protoplasmic and contain a 

 nucleus. This forms what is called the Malpighian layer. 

 In the superficial part the nuclei of the cells disappear, and 

 the cells gradually become hard and horny. This forms what 

 is called the corneous layer. The dry scales at the surface 

 are gradually worn away and shed. The flattened cells below 

 these are pressed up to the surface as new cells arc formed by 

 the division and multiplication of the cells of the deeper layers. 

 The dark colour of the skin of the negro is due to granules 

 of a dark pigment in the lowest cells of the Malpighian layer 

 of the epidermis. The Malpighian layer is firmly attached 

 to the dermis, but the corneous layer, as in a blister, may 

 separate from the Malpighian layer. 



The dermis, or corium, on which the epidermis rests, con- 

 sists of a fine but strong network of connective tissue, in which 

 a large number of yellow elastic fibres, many fine, but some 

 coarse, are mixed with the white fibres ; connective tissue cells 

 are also present in it. The surface of the dermis is not even 

 but thrown up into a number of small conical processes which 

 project into the epidermis, and so make the lower edge of the 

 epidermis irregular. These processes are called the papillae 

 of the dermis. The outline of the epidermis does not follow 

 the outline of the papillae, so that these are not evident at the 

 surface of the skin. Besides the papilla: the dermis, and with 

 it the epidermis, is thrown up into comparatively large ridges 

 easily seen by the naked eye, and in many places the skin is 

 folded and creased. 



The deeper part of the dermis is connected to the tissues 

 under the skin, such as muscle or bone, by a very loose 

 connective tissue of varying thickness, spoken of as the 

 subcutaneous tissue. This usually contains a considerable 

 quantity of fat, filling up the inequalities left by structures 

 below and giving roundness to the limbs. This layer is 

 particularly thick under the skin of the abdomen. 



