MAMMALIA. 393 



places are called callosities. The end of the snout and the under surface 

 of the toes want the hair in most of the mammals. The Cetacea have no 

 hairs at all, and the SirenidcB only at the margin of the snout and eyelids. 



Often the color changes according to the age, the climate, the locality, 

 and the season of the year. In domesticated animals the color of the hair 

 undergoes quite as many variations, and becomes also often longer or 

 shorter, or it crisps like wool, although the hair may have been straight in 

 the original stock of their race. Many mammals are provided with append- 

 ages on their forehead, which may be presented under three types : horns, 

 as in sheep and oxen ; antlers, as in deer ; and agglutinated hairs, as in the 

 giraffe and rhinoceros. Horns proper are so placed as to cover a horn 

 core, a projection of the frontal bone. They increase in size every year, 

 without being ever shed, and usually occur in both sexes. They are found 

 in oxen, sheep, goats, antelopes, chamois, &c. 



T^ie horns of deer are more properly termed antlers, in French called 

 bois, or wood. These are entirely solid, and are shed every year, to give 

 place to a larger pair. The female rarely possesses them ; an exception 

 is, however, found in the reindeer. The annual shedding and growth of 

 the horns is very curious and interesting. We take the example of the 

 deer, according to Bell's History of British Quadrupeds. " Let it be stated 

 first that the horn is placed upon a protuberance on each side of the frontal 

 bone : the part which rests upon the bone, forming the base of the horn, is 

 surrounded by a rough protuberant ring called the burr. Now the principal 

 stem of the horn has the name of the beam ; the irregular divisions near its 

 extremity are termed branches, and are distinguished from the true antlers, 

 which are the essential branches belonging to the species, and stand gene- 

 rally forwards, of which the first is called the brow-antler, the next the bez- 

 antler, and the third the royal ; the crown is termed the surroyal. By the 

 number of these antlers, and other marks in the development of the horns, 

 the age of the animal may be nearly ascertained. The growth of the horns 

 is an astonishing instance of the rapidity of the production of bone under 

 particular circumstances, and is certainly unparalleled in its extent in so 

 short a period of time. A full grown stag's horn probably weighs twenty- 

 four pounds, and the whole of this immense mass of true bone is produced 

 in about ten weeks. During its growth, the branches of the external caro- 

 tid arteries, which perform the office of secreting this new bone, are con- 

 siderably enlarged, for the purpose of conveying so large a supply of blood 

 as is necessary for this rapid formation. These vessels extend over the 

 whole surface of the horn as it grows, and the horn itself is at first soft and 

 extremely vascular, so that a slight injury, and even merely pricking if, 

 produces a flood of blood from the wound. It is also protected at this time 

 with a soft hairy or downy coat, which is termed the velvet ; and hence 

 the horns are said to be in the velvet during their growth. When com- 

 pleted, the substance of the horns becomes dense, the arteries become obli- 

 terated, and the velvet dries and falls off in shreds, a process which is 

 hastened by the animal rubt)ing his horns against th*e branches of a free. 

 The horns remain solid and hard, constituting the most effectual weapons 



597 



