170 
Bones are clothed externally by a membrane 
termed periosteum; this membrane serves as a 
matrix in which bloodvessels ramify before enter- 
ing the compact tissue of bone, It must be re- 
membered that bone is not only dependent on 
the periosteum for nutrition, but the deeper lay- 
ers of this membrane have bone forming prop- 
erties; the increase in thickness of a long bone 
is due entirely to the periosteum. Should the 
periosteum be injured, and inflamation become 
established, a local increase in its bone forming 
function is the result, by over nutrition of the 
bone furming cell, producing a rounded or ir- 
regular swelling, termed anode, In some cases 
the periosteum is so damaged that it becomes 
detached and as a consequence the bone be 
neath dies. 
those parts of the living bone adjacent, become 
As soon as a piece of bone is dead, 
unusually active, !eucocytes or white-blood cells 
begin to devour and succeed in detaching the 
dead portions when large, or completely digest 
ing them when small. 
Dead boneis known by the following features; 
it has no sensation, emits a sound when struck 
with a metallic instrument, and it does not bleed 
when cut. 
Now, che antlers of a deer when young and 
growing, are covered with a soft. vascular mem- 
brane, which is beset with delicate downy hairs 
and also has a number of secreting glands in its 
substance. This membrane termed the 
<‘velvet,” and it bears the same relation to the 
is 
growing antlers as the periosteum does to bone. 
As long as the antlers retain this velvet in a liv- 
ing to grow, 
to increase in length and thickness. When the 
antlers are growing they feel warmer to the 
touch than the rest of the body, resembling in 
When the antlers 
condition, they continue 
this respect an inflamed part, 
are ‘‘in velvet” a stag is particularly careful not 
to knock or rub the antlers, for they are very 
sensitive, and when he is so unfortunate as to 
bruise them, anode or swelling, forms upon them, 
in every way like the nodes or swellings upon 
other bones when they become injured. After 
the antlers have attained full dimensions, it is 
difficult for the circulation to be maintained 
through so thin and delicate a membrane as the 
THE OREGON NATURALIST. 
‘‘velvet” and asa natural consequence it shrivels 
and peels off; the bone beneath becomes deprived 
The branches of the antlers 
At this stage 
the antlers become powerful weapons, and the 
of blood and dies. 
suffer first and then the beam. 
stag, instead of taking every precaution not to 
knock or bruise them, now fears nothing, for 
In 
time the necrosis extends along the antler, until 
they are dead bone, devoid of sensation, 
it reaches the pedicle — that part which is 
covered with the natural hairy skin of the deer, 
In course of time a line of demarcation is 
formed by leucocytes and the antler falls by a 
process exactly analogous to that by which a 
piece of dead bone is separated. 
We may turn to theconsideration of processes 
in disease which are dominated by the physio!o- 
gical process pecu'iar toa particuiar animal ,and 
illustrate this by reference to cutaneous horns, 
especially that form of horns which arises from 
the mo.lification of warts. Not infrequently in 
many mammals and birds the free portions of 
warts bscome readily and easily transformed in 
a tissue identical witha horn. Sucha specimen 
was procured by the celebrated John Flunter. 
It shows a large horne, projecting from the fore- 
heid of a cow. The horn is fifty centimeters 
in length and is preserved in the Museum of the 
Royal College of Surgeons, A careful examin- 
ation of the horn and of the material which 
occupied the cavity in the horn, indicate that it 
originated in a wart, 
Such horns are somewhat common in man 
and have been known to attain a large size. 
A phystologica/ type of such horns is furnished 
by the nasal horn of the rhinoceros, which in its 
structure, connections and mode of origin, re- 
sembles in its main particulars, the pathological 
horn on the head of the cow, 
Birds not unfrequently exhibit this peculiarity 
of wart horns and an example growing from the 
leg of an oyster catcher was Seen by the author 
Such 
horns in birds, follow the course of avian dermal 
organs in general and are usually shed at the 
jn a dried skin, in a private collection. 
moult. (To be continued.) 
C. C, PurRDUM. 
