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THE SKIN. 151
ones upward into the bulb, where a special action takes place, some
going to form hair, others nails, etc. etc. They form the hair : the
great bulk of the cells become elongated and spindle-shaped, and
form what has been described as the fibrous substance of the shaft.
The Sudoriferous or Szceat Glanch (Fig. 76) are distributed over
nearly the entire surface of the body. They are most numerous in parts
not supplied by hair, though they are plentiful in parts where the
growth of hair is abundant, their ducts occasionally emptying into the
hair-follicle. Krause has estimated the entire number distributed over
the body to be 2,381,248, or from 400 to 600 to the square inch on the
lower limbs, back of the neck, and trunk, where they are fewest, while
in the palms of the hands and on the soles of the feet they are found
in their greatest number, and reach 2800 to the square inch.
The length of the sudoriferous gland, together with its tube, has been
estimated to be about a quarter of an inch. This gives the human body,
containing as it does 2,381,248 such glands, about fifty thousand feet, or
over nine miles, of perspiratory tubing.
The size of the sudoriferous glands varies in different parts of the
body, those in the axilla being the largest. Here they have been
found about a sixth of an inch in diameter, though their averag-e diam-
eter ni this region is from one-thirty-sixth to one-twelfth of an inch, tlie
average over the entire body being one-seventieth of an inch.
Duct of the e Sweat-sland within the epithelial layers of the skin: BP. papilla with injected bloo
;
y granulated epithelia. deeply stained with carmine; /', diiqt with corkscrew windings in
coarsely ^
the epidermal layer (liiagnitied 20u diameters)
These glands eliminate a large proportion of the aqueous and gaseous
matter from the body. Under ordinary temperatures, in the absence of
too severe physical exercise, perspiration goes on imperce])tibly, but in
warmth and the stimulus of vigorous bodily exercise there is a percepti-
ble and more or less profuse flow.
These glands are situated in the lowest stratum of the corium, and
