6 E VOL UTION AND DISEASE. 



rounded or irregular swelling termed a node. In some 

 cases the periosteum is so damaged that it becomes 

 detached, and as a consequence the bone beneath dies. 

 As soon as a piece of bone is dead those parts of the 

 living bone adjacent become unusually active, leucocytes 

 or white-blood cells begin to devour and finally succeed 

 in detaching the dead portions when large, or digest 

 them completely when small. Dead bone is known 

 by the following features it has no sensation, emits a 

 sound when struck with a metallic instrument, and does 

 not bleed when cut. 



The antlers of deer when young and growing are 

 covered with a soft vascular membrane, beset with 

 delicate downy hair and glands, termed the " velvet," 

 which bears the same relation to growing antlers that 

 periosteum holds to bone (fig. 2). As long as the 

 antlers retain this velvet in a living condition they 

 increase in length and thickness ; when the antlers are 

 actively growing they feel warmer to the hand than the 

 rest of the body, resembling in this respect an in- 

 flamed part. When in " velvet " a stag is particu- 

 larly careful not to knock the antlers, for they are very 

 sensitive, and when so unfortunate as to bruise them, 

 a node or swelling forms upon them in every way 

 resembling nodes on other bones when injured. I have 

 seen nodes on antlers, caused by blows, as large as 

 oranges. This is illustrated in fig. 3, which is a drawing 

 of a pair of antlers of a roe-deer preserved in the 

 museum of the Royal College of Surgeons. The left 

 antler is shorter than the right one and has an ossified 

 node upon it as large as a Tangerine orange. After the 



