These affections differ only in this, that in the latter the earthy matter is not deposited originally, whilst in the former it is absorbed after having been deposited; in both the result is the same. The latter is peculiar to the very young, the former to those of an advanced age.[11] Rickets and mollities ossium seem to differ also in this. In the latter there is seldom, if ever, any reparative action. The diseased process of deposit continues in the bone, the softening increases, and the patient ultimately perishes. Whereas, in rickets, the softened and yielding state of the bones is only temporary: after a time earthy matter is deposited in due quantity, and the bones become compact, firm, and solid, capable of supporting the weight of the body, though necessarily permanently bent and deformed, if proper means have not been employed during the softened condition. The thickness of the rickety bone, as Mr. Stanley has shown, takes place on the concavity, which is the situation where the greatest strength may be added with the least expense of new matter. In the same way the reparation of fractures not accurately adjusted goes on most actively in the concavity formed by their displacement. [Illustration] Softening of the bones is met with at all ages, and in different degrees. It seems sometimes to be congenital, and combined with hydrocephalus. It often follows dentition, measles, hooping-cough, or other infantile diseases inducing debility. In females it seems to be produced, or at least often accompanied, by the debilitating effects of leucorrhœa, miscarriages, and floodings. Loss of blood, in any way, predisposes to it. Mercury, given in immoderate quantities, produces a softening of the bones; and, in some most remarkable instances on record, the free use of common salt was the only cause assigned. When the disease affects children, all the bones generally suffer, those of the extremities as well as those of the trunk; the limbs become bent in an extraordinary manner, and the heads of the bones are swollen, and appear to be much more so in consequence of the wasted and flabby state of the muscles. The child walks with difficulty, and in many cases the legs are utterly incapable of supporting the weight of the body, so that he cannot remain in the erect position. The chest and pelvis become deformed, breathing is oppressed, the digestive organs are deranged, and the belly is tumid. The bones of the limbs become flattened as well as bent, and in their concavities, as remarked in the preceding cut, new bone is effused, in order that the column of support may be thereby strengthened. The new deposit is of extremely dense consistence, and is effused in greater or less quantity, according to the degree of curvature.