32 THE ANTELOPE OF AMERICA. 
It will be observed, on examining Fig. 1, that the outer part 
of the skin 6, presents an irregular corrugated appearance, occa- 
sioned by protuberances and depressions, called papille, varying 
considerably in height and depth. With this uneven surface 
terminate those blood-vessels of the skin which carry the red 
blood in sufficient quantities to produce a stain. Upon this un- 
even surface rests the epidermis, or the outside coating of the 
OF AN INCH X 296. 
339 —————— oF an incu x 69. aoo0 
Thin section of a growing horn of an antelope, cut perpendicular to the surface. 
Fie. 1 shows the general structure under a low power. Fra. 2, more highly magni- 
fied, shows the cell structure. The letters refer to the same parts in each figure. 
a. The connective tissue continuous with the periosteum of the core of the horn. 
6. The papille, very large and irregular. 
c. The cell growth upon the papille. 
d. The outer portion, seen to be made up of the flattened and desiccated cells of the 
layer beneath, alrcady converted into horn. 
skin. If this appears to want uniformity of structure, a critical 
examination shows that this results from a change of form of the 
cells of which it is composed, which become flattened and consol- 
idated by compression, and by evaporation, or by becoming dried 
up. Thus is the epidermis converted into true horn. Chem- 
ically, the constituents of epidermis and of horn are nearly iden- 
tical. The true horn at d is but the flattened and dried up cells 
which were formed upon the papillew , and were pushed up by 
new cell formations beneath them, till they reach their final form 
