EXOSTOSIS. 489 



increase of the secretion of bony matter. It is to the peri- 

 osteal exostosis, or cartilaginous exostosis of the perios- 

 teum, that those bony swelhngs we call splints, spavins, &c., 

 owe their origin. Yet these exostoses are not limited to 

 any individual parts, but can be as numerous as the bones 

 themselves : the spine exhibits them throughout ; the ex- 

 tremities have them from the semi-ossified cartilage of the 

 senile scapula to that of the lateral cartilages of the coffin 

 bone. The causes of sequine exostosis may be characterized 

 as predisposing and proximate. Pressure is the predisposing 

 cause, and inflammation the proximate. If the exertions 

 are pushed greatly beyond an ordinate degree, the neigh- 

 bouring muscles press unduly against the bone, irritation 

 springs up ; commencing occasionally within the periosteal 

 covering, but oftener within the ligamentous connexions 

 around. After a time, and with repetitions of the original 

 cause, inflammation sets in, and communicates itself to the 

 periosteum, which is in contact with the bone. But there 

 are, as already hinted at, injuries productive of exostosis 

 where the stimulus is one violent effort of over straining 

 the bodily machine : here we have reason to suppose that 

 the foundations of the most ruinous exostoses are laid within 

 the ligaments, which inflaming, extend the affection to the 

 periosteum, and from thence to the bone under it : the 

 result is, that osseous union takes place between the liga- 

 ments and the contiguous bone, of which spavin is an in- 

 stance. The articular cartilages are particularly exposed 

 to the effects of pressure ; as those of the spinous processes 

 of the vertebrae also are ; those of the lateral parts of the 

 feet, and some others are likewise the centres for osseous 

 deposits : during which the cartilage may become absorbed, 

 leaving the bony matter. A morbid disposition to ossific 

 deposit likewise appears to pervade other parts than those 

 immediately connected with the bony base ; as within the 

 coats of the large arteries, the cartilaginous parts of the 

 larynx and the internal portions of some glands. In horses 

 the order of science is so far destroyed, that it is not un- 

 usual to see ulceration and deposition going forward side 

 by side, on the same part of the same bone ; as in the arti- 

 cular surfaces, where disease generally ends in anchylosis. 

 The cure of exostosis must consist in whatever stops the 



