MAMMALS 81 



periosteum were torn off in strips as they are at the present 

 day. The formation of the burr was probably the result of 

 this, for the injured blood-vessels at the base would continue 

 to deposit bony matter after this process was stopped on the 

 surface of the naked antler. 



We have then reached the condition of the bony antler 

 stripped of skin and periosteum: what takes place afterwards? 

 According to J. D. Caton, after the periosteum has gone, there 

 is still a considerable blood supply passing up internally from 

 the pedicle, and internal ossification of the antler proceeds. 

 The interior, however, does not become completely solidified : 

 a thin solidified plate of bone is formed at the level of the 

 burr and this ultimately cuts off the supply of blood, by 

 closing the apertures through which the internal blood- 

 vessels pass. At this stage the pedicles are carrying masses 

 of dead bone. These are cast off, not irregularly or accident- 

 ally, but by a regular process. Caton states that the blood- 

 vessels which pass in from the periosteum of the pedicle into 

 the " articulation " of the antler perform the function of 

 absorbing bony tissue until the connection between the antler 

 and the pedicle is destroyed, and the former drops off and is 

 detached by a slight blow. We do not know whether the 

 shedding of the antler was from the first an annual process, 

 or whether it occurred originally at longer intervals, and 

 afterwards became annual. The case of the sambar, if it is 

 true that it does not shed its horns every year, would support 

 the latter conclusion. But it seems reasonable to suppose 

 that the absorption process to which the shedding is due was 

 the necessary physiological result of the loss of the periosteum 

 and gradual death of the antler. The commencement of the 

 process may be determined either by the cessation of vitality 

 at the base of the antler, or by the lowering of vigour in the 

 whole body which follows the rutting season, an exhaustion 

 partly due to the preceding excitement and expenditure, 



