242 ZOOLOGY. 



tain age there appears a growth of bone on the frontal bone, 

 resembling what medical men call an exostosis, or .the 

 callus of fractured bones. These protuberances, which are 

 very compact, grow rapidly, and carry the integuments 

 with them ; they are also very vascular. After a time, a 

 series of osseous tubercles begin to form around the base 

 of the osseous horn, which increasing, obliterates the blood- 

 vessels, thus cutting off the supply of blood to the integu- 

 ments covering the antlers. The integuments drop off con- 

 sequently, and disappear, leaving the antler itself exposed. 

 And now the antler itself dies, as it were necrosed, and ends 

 by being detached from the cranium. In twenty-four hours 

 after this, a thin pellicle covers the surface from which the 

 antler had been detached, and soon a new prolongation begins 

 to grow in the place of the one which has been shed. Gene- 

 rally, the new antler is greater than that to which it succeeds, 

 and its branches are larger and more numerous ; but it is of 

 no longer duration than the first, and it undergoes the same 

 changes. 



With one exception, the reindeer antlers grow only in 



Fig. 202. Head of the Goat. Fig. 20^ Head of the Elan, or 



'Northern Elk.* 



the male. The phenomenon has obvious S3 7 mpathies with 

 the organs of reproduction, for they persist for more than 

 a year in those animals in which the rut does not corne to 

 a crisis and is limited. It is periodic, and occurs in the 

 spring. 



394. The extension of the nose in the elephant into a 



* This must not be confounded with the Eland of South Africa, which is 

 an antelope. 



