ON THE GROWTH AND DEVELOPMENT OF HORNS. 
67 
modification of hair. All other horns are placed in pairs, or one on each side of 
the median line. One species of Rhinoceros has only one horn, which is placed 
over the end of the nose, and exactly in the middle line. The other species has 
two horns, but they are placed one above the other, still retaining their central 
position. The second or posterior horn is much smaller than the other. They 
are not deciduous. 
II. Those found on the Giraffe. These are horns of the most simple kind, but 
are not true horns, as no horn enters into their composition; yet from their 
situation and shape they have received the name, and therefore I shall consider 
them as such. They are simple bony processes from the os frontis , which are at 
first a little moveable in bony sockets, but soon become fixed and immoveable. 
They also differ from other horns in being covered with skin, and in having little 
tufts of hair on their extremities. They are found on both sexes, and are not 
deciduous. 
III. Those which are found on some of the Ruminants, and which are formed 
on bony processes from the os frontis , which are at first moveable, but after¬ 
wards become fixed. These bones are covered with a highly vascular membrane, 
which secretes the horn or hard external cuticle. The horny part grows by 
lamina which are formed on the inside by the vascular membrane covering the 
bone. This horn has no vascularity itself, and cannot be made to receive any 
injection. Those animals whose horns grow most at particular seasons, as the 
Sheep, have the cuticular or horny matter thrown out most at those times, and 
as more is secreted than is necessary for its increase in length, it is disposed of in 
thickening the part last deposited, and thus rings come to be formed which bear 
a certain relation to the age of the animal. In others, as the Ox, they grow 
more regularly, and therefore the fibres appear to be longitudinal. The essential 
distinguishing mark of these horns is their being supported on, and being filled by, 
bone, and in their not being deciduous. 
Many races of sheep have horns on both sexes. Others have them only on the 
males. In the Iceland Sheep they vary in number from four to eight. In the 
Moufflon, a species of Sheep, the horns are of immense size, the pair sometimes 
weighing 20 pounds. In the Goat family horns are found on both sexes, but larger 
in males than females. In the Ibex the horns weigh from three to four pounds 
each. All the Antelopes have horns of this class, which vary somewhat in form, 
and in the direction they assume. These horns are also found in all the Ox family. 
In the Common Ox the horns are larger in the female than in the male, but the 
texture is less dense and firm. In the Buffalo they are very large, often mea¬ 
suring five feet or more from tip to tip. 
IV. Those called antlers, such as are found on the Stag, Deer, &c. These, 
besides being weapons of defence, are highly ornamental to the animals]; they are 
vol. hi.—NO. XVII. 
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