In the arteries of the limbs calcareous depo. sition may likewise commence in the middle coat itself, which becomes harder and thinner as the disease advances.
It is important to observe that the close examination of calcareous plates through their various phases of development demonstrates, as we have seen, their independence of inflam mation.
Calcareous deposition is remarkably depen dent upon age. Bichat calculated that the arteries of seven of every ten persons beyond the age of sixty were thus affected ; while its existence is extremely rare in early youth. Writers have indeed maintained the perfect immunity of the vessels of youthful subjects from this change : but Mr. Young found the temporal artery of a child fifteen months old converted into a calcareous cylinder ; Otto* once discovered incipient ossification of the aorta in.a. girl of seventeen; Wilson met with a similar condition in a child three years old; Andral in a girl aged eight; and numerous other instances of the kind are recorded. Cal careous deposition is more common in vessels of a large than of a small calibre, and espe cially in the aorta ; rarer in the upper than the lower extremities ; it sometimes extends through the entire arterial system of the trunk and lower limbs,— we have before us the ves sels of a subject in this condition, who died with gangrcena senilis.* Such disease never occurs, according to Otto, in the arteries of the thoracic and abdominal walls, and perhaps those of the alimentary canal and liver ; and is, on the contrary, common in those of the pelvis, of the brain, of the thyroid gland, the heart, the spleen, the kidneys, &c. The pul monary artery is, comparatively speaking, con sidered exempt from calcareous deposition : several instances, however, are referred to by Otto, in which it was more or less completely " ossified ;" it is not unfrequently so where the right and left cavities of the heart com municate, (but here the vessel is placed in re spect of its contained fluid in the state of an ordinary artery). Hope t attended a lady, aged 60, in whom the " pulmonary artery was found quite ossified where it plunged into the lungs ;" and from our own records of cases we know that slight alteration is not very uncommon.
The close comparison of corresponding ves sels on the two sides of the body has led M. Bizot to the discovery that not only the same vessels, but the same parts of these, are, with the rarest exceptions, affected with the same alterations of structure,—that a law of sym metry regulates the development of these. Upon this point much curious information will be found in M. Bizot's admirable essay.
Calcareous deposition is common in the ar teries of syphilitic subjects, and of' those who have taken mercury to excess. Much fanciful hypothesis has been indulged in respecting the influence of certain kinds of diet on its pro: duction.
This tnorbid state destroys the elasticity of the arteries, renders them fragile, and inter feres with the circulation ; we have known it lead to rupture of the aortic valves. The cal careous matter protruding more or less into the vessel affords a centre for the blood to coagulate around, and may lead to its com plete obliteration, — a result which it would appear may be produced by mere thickening of the coats ; in either case suspension of the circulation and gangrene are the results. " Ossification " of the coronary arteries of the heart has been met with in cases of angina pectoris (recently by ourselves) and of sudden death, — probably rather acting as the occa sion, than the cause, of both.
(2.) Central. (Arteroliths.) — Calcareous concretions, free in the interior of the arteries, , are as rare as the conditions which we have just described are common. Ottot saw in the Copenhagen Museum " a round stone as large as a pea," said to have been taken from the spermatic artery ; but he believes it to have probably been of venous origin. Eight loose stony concretions have, he observes, been met with in an aneurismal sac* ; the largest of these was as big as a plum. Landerer has recently analyzed an aortic concretion, which contained 14 per 100 of uric acid.t Veins. — Parietal concretions are as rare in the veins as coininon in the arteries ; central concretions as frequent in the former as rare in the latter vessels.