ON THE GROWTH AND DEVELOPMENT OF HOKNS. 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, hut they are placed one ahove 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. III. — no. XVII. L 



