42 THE MUCOUS MEMBRANE AND SKIN. 
THE SKIN. 
Of how many layers does the skin consist ? 
Three: Epidermis or scarf skin; cutis vera or corium, and the 
subcutaneous layer. 
Of what form of epithelium is the epidermis made up and into 
how many layers is it divided ? 
It is composed of stratified epithelium and is divided into four 
layers, viz.: Horny layer, stratum lucidum, stratum granulosum and 
Malpighian layer or rete mucosum. 
Describe the Malpighian layer. 
The deeper cells of this layer are elongated and placed perpendicular 
to the surface of the corium with which they are in contact. The 
remaining portion of this layer is composed of roundish or polyhedral- 
shaped cells. These cells have fine channels between them bridged 
across by fine processes passing from cell to cell. These cells are 
called spiny or prickle cells. The pigment is contained in this layer. 
What is the rete Malpighi ? 
If a section of the Malpighian layer is made parallel to the surface 
of the skin and cutting through the tops of the papilla of the corium 
which extend up into this layer, a network composed of certain of the 
cells of the Malpighian layer is seen. This network is called the 
rete Malpight. 
Describe the other layers of the epidermis ? 
The cells next above the Malpighian layer become filled with 
granules and are called the stratum granulosum. Next above this 
layer the cells appear to have become clearer, and their outlines and 
nuclei indistinct. This is the stratum lucidum. The external or 
horny layer is composed of hard, flat scales showing no nuclei. These 
scales are modified cells that have been derived from the deeper layers. 
As the epidermis is non-vascular, the cells as they approach the 
surface become desiccated and are thrown off, successive layers forming 
below to take their place. 
What layer contains pigment and gives color to the skin as in the 
negro ? 
The deeper layers of the rete mucosum. 
What is the structure of the corium ? 
It is a sentient, vascular, fibrous layer, made up principally of inter- 
lacing bundles of white fibrous tissue among which ramify bloodvessels, 
