The bones of rickety subjects are soft, cellular, and of a brown colour, contain a dark fluid, and are very deficient in earthy matter. As a simple proof of the latter circumstance, it may be mentioned that distortions of the pelvis can be, and often are, accurately imitated by soaking the bones for some time in acid, whereby the earthy matter is extracted. In many instances this component of the bones is almost entirely removed, and soft matter deposited instead; they then consist merely of an extremely thin external osseous shell, covered by thickened periosteum, and containing a pulpy substance resembling fatty matter. During the progress of the disease, the urine deposits, often in great quantity, a white sediment, which, on analysis, is found to be the phosphate of lime. In rickets the head is generally enlarged to a greater or less degree, and the bones of the cranium are thickened and spongy; not unfrequently the intellectual faculties remain acute. In adolescents and adults the limbs seldom become affected; the bones composing the spinal column are the seat of the disease, and, along with the distortion of the spine, the position of the ribs is necessarily altered. Certain rare cases have occurred, in which all the bones of the adult were softened to a very great degree. In one remarkable instance, the patient complained of an annoying sense of tightness in the limb most affected, and, on examination, the softened bone was found greatly depressed at that point, as if a strong ligature had been drawn tightly round it. Mr. Howship, who attended the patient, was so kind as to present me some years ago with a portion of the altered femur, which consists of a fatty-looking substance, and appears to contain little or no earthy matter.[13] Though incurvation of the spine occurs in boys, and even in adults, still it is most frequently met with in young females; and in them it is often induced by their having assumed a bad habit by sitting long in one constrained and awkward posture, as in writing or drawing, without, perhaps, the bones being unnaturally soft in the first instance. It often follows affections of the lower limbs, as of the knee or hip-joint; and is also caused by shortening of a limb, which has been negligently or ineffectually treated after fracture during childhood, or by the patient being allowed to continue a custom of standing awkwardly on one leg. In a very remarkable specimen in my possession, the curvature seems to have resulted from the tremendous enlargement and consequent weight of the head. The whole skeleton (head, thorax, pelvis, and extremities) is deformed, flattened, and twisted. This may have arisen more readily in consequence of the atrophy of the bones, and retardation of their growth, produced by the long confinement to bed. The number of ossa triquetra in the lambdoidal suture was unusually great. The patient attained the age of twenty-five. The affection commenced from birth. [Illustration]