MAMMALIA. 



375 



Head of Goat. 



from which circumstance the animals of the Deer tribe are 

 termed Solid- horned Ruminants. The quantity of bony matter 

 thus annually secreted is very remarkable. In the large 

 extinct species, popularly known as the "Irish Elk," the 

 Antlers weighed from GO to 70 lbs. and as in the existing 

 males, were the growth of 

 a single year. In the Ox 

 and the Goat {Fig. 295), 

 these organs are formed of 

 the elastic substance which 

 we call horn, and which is 

 analogous to that of the hair 

 and hoofs. They are hollow 

 within, cover the bony axis 

 like a sheath, and "continue 

 to grow throughout life, but 

 only at intervals, depending 

 upon the season of the year, the age of the individual, and 

 the supply of food."* To these animals the name of Hollow- 

 horned Euminants has been applied ; the bony core of the 

 horns is formed of cells, which communicate with the nose, 

 and are thus filled with air 

 is added to strength. 



The tusks of the Elephant, though appendages exterior to 

 the head, are in reality a part of the dental system of the 

 animal, and are the representatives of those teeth which in 

 man are known as the cutting or incisors. " They not only 

 surpass all other teeth in size, as belonging to a quadruped so 

 enormous, but they are the largest of all teeth in proportion 

 to the size of the body."t Tusks of the Mammoth, an extinct 

 species of Elephant, have been found from nine to eleven feet 

 in length, and one has been known to weigh so much a-s one 

 hundred and sixty pounds. The importance of these tusks as 

 an article of commerce may be estimated from the fact, that 

 in 1737, an account was published of the Mammoth's bones 

 and teeth found in Siberia ; and of the uses to which the 

 tusks were applied ; and *' from that time to the present there 

 has been no intermission of the supply of ivory furnished by 

 the tusks of the extinct Elephants of a former world. ''^ 



By this arrangement lightness 



* Ogilby. Monograph of the Hollow-horned KuminanU, 

 of the Zoological Society of London, 

 f Owen's Odontography. J Idem. 



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