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POPULAR SCIENCE 'REVIEW. 
fluence of cold, and known as the “ goose-skin,” is due also 
to their contraction. 
Hair is almost universally the covering of the skin in the 
class of Mammalia, and is found even in the whale, hut only in 
the shape of a few scattered hairs here and there over the body, 
so that it can be of no use except to carry out the type of 
the organisation of the class. In certain parts of the bodies of 
some animals hairs sometimes become remarkably developed 
and strangely modified, as is the case in the hedgehog and 
porcupine, where they assume over the greater part, but not the 
whole of the body, the form of spines and quills. 
In the class of birds hair is not found, being replaced by 
feathers, and the apparent hairs on animals of this class, on 
being examined with a microscope, present the characters of 
feathers, and not those of hair. 
We have thus sketched the principal characters of that beau- 
tiful organ, the Skin, which, it is hardly necessary to observe, 
is as completely illustrative of the Creator’s skill and wisdom 
as is every other portion of the animal frame. 
EXPLANATION OF PLATE XVI. 
Fig. 1. Vertical section through skin of thumb. 
a. Horny layer of epidermis ; b, its mucous layer ; c, the corium ; d, 
fat globules ; e, sudoriparous glands ; /, their canals ; i, sweat- 
pores. 
Fig. 2. Compound papilke, from the hand. 
Fig. 3. Section through the skin, from the leg of a negro ; a, horny layer of 
epidermis ; b, mucous layer ; r, coloured cells of the mucous layer ; 
d, papillae. 
Fig. 4. Termination of a nerve in a Pacinian corpuscle, from the hand ; a, 
nerve ; b, envelope. 
Fig. 5. Perpendicular section through the scalp, with two hair-sacs ; a, 
epidermis ; b, muscle of the hair-follicle ; c, cutis. 
Fig. 6. Under-surface of the epidermis, from the palm, showing the depres- 
sions in which the papillre were lodged, and the sudoriparous ducts 
attached. 
Fig. 7. Section through the skin, near the ear. a, horny layer of epidermis ; 
b, sebaceous glands ; c, canal of ; /, ceruminous glands ; d, hair 
follicle ; g, fat globules. 
Fig. 8. Hair-sac, from the face, with several specimens of Demodex follicU - 
lorum attached. 
Figs. 9, 10. Demodex follimlorum. 
Figs. 1 — 7 are after Kolliker (Hum. Hist.) 
Figs. 8—10. E. Wilson, in Proceedings of Hoyal Society. 
