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PRODUCTS OF THE EPIBLAST AND MESOBLAST. 559

of hairs is seen in the pig 3 cm. in length or in hnmun fetuses between
the third and fourth months. The infant cells of the rete Malpighu
Fig. 305.

Commencing Replacement of Old
Hair-follicle in Longitudinal Section: (/.mouth by New Hair (Toldt) : ", outer
of follicle; 0, neck; ., bulb; root-sheath ; b, dermic coat of fol-
^, outer root-sheath: ;/, inner root-sheatli /-, licle' ; f, down growth of epithe-
m, adipose
hair; /;, its medulla; /, hair-knob; p, lium to form new hair-follicle; p,
o, papilla of skin:
tissue; n, hair-musde ; continuous papilla of new hair commencing;
papilla or hair; 6-. vete mucosura ./, root of old hair; t, duct of seba-
with outer root-sheath; fp, horny layer; I, seba- ceous gland.
ceous gland.
this thickening proceeds until they
appear to thicken at many points ;
dip into the underlying corium. The cellular activity does not lessen