In one sense, the osseous tissue that is formed in regeneration of destroyed or frac tured bones may be regarded as due to a morbid, although a restorative action. Hyper trophy of bone is by no means rare, being sometimes local, forming a protuberance on the external surface, in which case it is termed an exostosis; and sometimes over the whole bone or over several bones, giving rise to the condition known as hyperostosis. Again, true osseous tissue occasionally occurs in parts in which, in the normal condition, no bone existed, as in the duramater, in the so-called permanent cartilages (as those of the larynx, ribs, etc.), in the tendons of certain muscles, and in certain tumors. The peculiar causes of the osseous formations which are unconnected with bone are not known.
Calcareous deposits or concretions not exhibiting the microscopical character of bone, but often falsely termed ossifications, are of no unfrequent occurrence. Analyses of such concretions occurring in pus, in the valves of the heart, in the muscles. and in the. lungs, are given by Vogel in his Pathological Anatomy of the Human Body; and in some• of these concretions the phosphate and carbonate of lime occur in nearly the same per centages as those in which they arc found iu bone. The diseased condition usually but incorrectly called ossification of the arteries,-is of sufficient importance tc require a brief notice. rn consequence of the deposition of earthy or calcareous matter in the middle
coat of the artery, the vessel loses all its elasticity, and becomes a rigid, unyielding tube. All parts of the arterial system are liable to this change; but it is more frequently met. with in the ascending portion and arch of the aorta, than in any other part of that vessel, and is more common in the lower extremities than the upper. The affection is usually partial, but occasionally it appeArs to be almost universal. Thus, Dr. Adams has recorded a case, in the Dublin hospital reports, in which no pulsation could be felt in any part of the body, and even the heart offered no other sign•of action than a slight undu lating sound. Old age strongly predisposes to this diseased condition, and probably few very aged persons are altogether exempt from it. There is also reason to believe that. gout and rheumatism favor these calcareous deposits. This condition-of the arteries may give rise to aneurism, to gangrene of the extremities in aged persons, and to atrophy, and consequent feebleness of the brain and heart. (The coronary arteries, which supply the heart with the arterial blood necessary for its own nutrition, are very often, although not, always, ossified in angina pectoris), Moreover, this condition of the vessels very mate rially increases the risk from severe accidents and surgical operations.