8 E VOL UTION AND DISEASE. 



and dies. The branches suffer first and then the 

 beam. At this stage the antlers become formidable 

 weapons, and the stag, instead of taking every precau- 

 tion not to knock or bruise them, now fears nothing, 

 for they are like dead bone, devoid of sensation. In 

 time the necrosis extends along the antler until it 

 reaches the pedicle, that part which is covered by the 

 natural hairy skin of the deer ; in due course a line of 

 demarcation is formed by leucocytes, and the antler falls 



>, 



FIG. 4. The head of a Cow with a large cutaneous horn. 



by a process exactly analogous to that by which a piece 

 of dead bone is separated. 



We may turn to the consideration of processes in 

 disease which are dominated by the physiological pro- 

 cesses peculiar to a particular animal, and illustrate 

 this by reference to cutaneous horns, especially that form 

 which arises from the modification of warts. Not in- 

 frequently in mammals and birds the free portions of 



