THE SKIN. 43 
lymphatics and nerves. There are also some elastic fibres in this 
layer. Upon its free surface the corium is beset with papilla which 
fit up into the under layer of the epidermis. . 
What is the structure of the subcutaneous layer ? 
The fibres of the corium become more loosely arranged and the 
spaces between them are filled with fat (panniculus adiposus). This 
layer serves to attach the corium to the parts underneath. In this 
subcutaneous layer are the sweat glands, hair follicles, and some of the 
nerve endings. 
How are the bloodvessels and lymphatics distributed to the skin.? 
They branch and subdivide in the subcutaneous layer, and send fine 
branches up into the papille of the corium. 
How do nerve fibres terminate in the skin ? 
They branch and subdivide in the subcutaneous layer. Some fibres 
may terminate as tactile corpuscles or Pacinian bodies in the true skin; 
some may be distributed to the hair follicles and glands of the skin, 
while others pass up into the Malpighian layer and seem to divide still 
further. The precise mode of termination of these ultimate nerve fibres 
has not been definitely settled. 
What are the nails and hairs? 
They are produced from the epidermis, and are modified growths of 
the horny layer. 
Describe the structure of the nail. 
It consists of a body and root, the former lying upon the modified 
Malpighian layer or nail bed. The root sets into a pocket of skin, 
the corium of which is called the matrix. The Malpighian layer at 
the root of the nail is thick, and gives a whitish color to the crescentic- 
shaped spot at the base of the nail, called the lunula. 
What are the points to consider in regard to hair? 
The shaft, root and bulb. The root and bulb are placed in 
oblique tubular depressions in the skin called hair follicles. 
What is the structure of the hair shaft? 
It is composed of three parts: A central or medullary portion, com- . 
posed of cuboidal or flattened cells loosely arranged. A cortical por- 
tion, made up of tough, flattened cells closely packed together, and 
having pigment granules of various colors in and between them. The 
outer layer or cuticula of the hair shaft is composed of non-nucleated 
scalelike cells, which overlap one another like scales on a fish, 
