82 
OSSEOUS TUMOUR. 
who got possession of the horse (an aged one) because it 
was unable to work, and the owner had destroyed it in con¬ 
sequence. 
Of these tumours I am not aware that any of our own 
authors speak; but Paget, alluding to them, says— 
“ These hard, osseous tumours are rarely found except in 
connection with the bones of the skull—sometimes, however, 
with the lower jaw—and are less rare amongst animals in this 
situation than in man ; their texture is very like that of the 
internal table of the skull, the petrous bone, or lower jaw.” 
Another writer, Rokitansky, thus describes them: 
“ Compact exostosis is the most frequent, and occurs on 
compact bones and parts of bones, particularly on the outer 
table of the cranial bones. It appears as if placed on the 
surface of the bone from without, and often separated from 
the bone by a furrow, which is generally narrow, and fre¬ 
quently deep, forming a fissure between the tumour and its 
basement, making the exostosis appear as if glued on, like a 
mushroom on a very short stalk. It often exceeds in 
density the bone whence it springs, and is then known as 
ivory exostosis. It is compact from the very first, and as 
the layers are added to it they at once become as dense as 
ivory. No spongy structure is found in them. The Haver¬ 
sian canals are small and far apart, and many of them sur¬ 
rounded by a distinct, well-defined, lamellar system. Some¬ 
times they are numerous in the same person.” 
“In the College of Surgeons Museum there is a specimen 
from the forehead of an ox. It is like a great spheroidal 
mass of ivory, measuring eight and half inches in diameter, 
and weighing upwards of sixteen pounds. Its outer surface, 
though knotted and ridged, is yet compact, like an elephant's 
tusk, and its section shows at one part a thin investing layer, 
like the bone covering ivory. It is nearly all solid, hard, 
close-textured, and heavy; only a few irregular cavities, and 
one with smooth walls, appear in its interior, and orifices of 
many canals for blood-vessels may be traced. Quekett found 
that it had a higher specific gravity than any bone, except 
what is found in the porcelain deposits on the head of bones 
affected with rheumatism. It has, how r ever, in every part 
the structure of true bone.” 
[Among the specimens of osseous tumours contained in 
the College Museum are three of the same description 
referred to in Mr. Cartledge’s communication. No. 1, the 
largest, weighs 8 lb. 7 oz., and measures in its long diameter 
10^ in., and 5^ in. in its short diameter. It is of a square 
