254 ON THE NATURE AND TREATMENT 
liable : I mean exostosis; but my principal object will be to 
advert to the nature of this disease as it appears on the meta¬ 
carpal bones, and which we term splent; and particularly to en¬ 
quire whether there be any analogy between the node in the hu¬ 
man subject and the splent in the horse. 
Exostosis, then, is an osseous tumour, which is not confined to 
particular bones, although some are much more subject to this 
disease than others. The bones of the extremities, and more 
particularly in the neighbourhood of joints, seem to be the prin¬ 
cipal seat of exostosis. 
Sir A. Cooper, I find, terms that species of exostosis which 
we have to attend to, cartilaginous exostosis of the periosteum. 
“It originates (he says) in an inflammation of the periosteum, 
and the corresponding part of the bone; and a deposition of 
cartilage of a very firm texture, and similar to that which forms 
the nidus of bone in the young subject, adheres to both these 
surfaces. 
“ The periosteum adheres to the external surface of the swelling, 
and the swelling itself is attached still more strongly to the surface 
of the bone. It continues, afterwards, to be secreted as the cartilage 
increases in bulk; for it appears that, between the periosteum and 
the bony mass, cartilage is constantly secreted, which constitutes 
the exterior suYface of the tumour. Thus, on dissection, we dis¬ 
cover, first, the periosteum thicker than natural; secondly, the 
cartilage immediately below the periosteum ; and, thirdly, ossific ( 
matter deposited within the cartilage, extending from the shell of ( 
the bone nearly to the internal surface of the periosteum; still 
leaving on the surface of the swelling a thin portion of cartilage ' 
unossified. When the accretion of these swellings ceases, and j 
the disease has been of long standing, they are found to consist, 
on their surfaces, of a shell of osseous matter, similar to that of 
the original bone, and of the same cancellated structure, and com¬ 
municating with the original cancelli of the bone. Consequently, 
when an exostosis has been formed in the manner here described, 
the shell of the original bone becomes absorbed, and cancelli arc 
deposited in its place; in the mean time the outer surface of the 
exostosis acquires a shell resembling that of the bone itself. 
When the exostosis has been steeped in acid, and by this means 
deprived of its phosphate of lime, the cartilaginous structure re¬ 
mains of the same form and magnitude as the diseased deposit; 
and, as far as I am able to discover, it is effused precisely in the 
same manner as healthy bone; from which it appears that the 
formation of these excrescences differs in no respect from that of 
the original bone, since they arc composed of cartilage for their 
