44 ORGANS OF DIGESTION AND ALIMENTARY TRACT. 
What is the root and what the bulb of the hair? 
The root is that portion continuous with the shaft that is in the 
hair follicle, and the bulb is the dilated portion of the hair where it 
ends in the follicle. The end of the bulb rests upon and surrounds, 
at the top and sides, a projection of the connective tissue wall of the 
follicle, called the papilla, 
What is the structure of a hair follicle ? 
The wall is formed first by a layer of connective tissue continuous 
with the corium of the skin. Within this is a thin, transparent layer 
called the vitreous membrane. Within this follicular wall is the root 
sheath proper, composed of two layers. The outer layer is formed by 
a dipping down into the follicle of the Malpighian layer of the epi- 
dermis. The inner layer is made up in turn of two other layers, of 
which the outer is composed of cells resembling those in the horny 
layer of the epidermis and is called Henle’s sheath. The inner layer is 
composed of polygonal or flattened cells, having elongated nuclei. This 
is called Hualey’s sheath, and belongs properly to the hair itself. 
What is the erector pili? 
It is a bundle of involuntary muscle running from the corium 
obliquely to the hair follicle, and which, by contracting, serves to raise 
the hair erect. 
Describe the structure of sebaceous glands. 
They are racemose glands, the alveoli of which are lined with large 
polyhedral cells. Their ducts, lined with polyhedral or flattened cells, 
open, as a rule, into a hair follicle near the surfacé of the skin. 
Describe the sweat glands. 
They are simple tubular glands lined with polyhedral or cuboidal 
cells, They terminate in the subcutaneous tissue, and at their point 
of termination are coiled up into a roundish mass, and are surrounded 
by loose areolar connective tissue. 
ORGANS OF DIGESTION AND ALIMENTARY 
TRACT. 
THE TEETH. 
Of what is a tooth composed ? 
Of three calcified tissues: Enamel, dentine and cement, or crusta 
petrosa. 
