This is essentially a disease of childhood, and makes its first appearance when the child begins to walk, about the eighteenth month after birth. It may come on in any of the earlier years of childhood, but it never occurs after twelve years of age. It is particularly the children of old or feeble parents, or the later children of a large family, and the children of the poor, ill fed, and living in small, badly-aired, and ill-lighted houses, that are most liable to the disease.
Its causes arefeebleorserofulousconstitution, and insufficient or artificial food, wanting in the necessary accessory foodstuff (see Vitamines, Vol. II., p. 141), and want of fresh air and light.
The chief defect in the bone is absence of the due proportion of animal and mineral matter, the mineral matter—lime salts—being deficien t, so that the bones are soft and yielding. Be sides this the process of development in the bones is more slow than is usual, and some stages of it are exaggerated, so that not only is there diminished quantity of lime salts, but also increased formation of the soft material, viz. cartilage cells. When at last the bone salts begin to be deposited the formation of bone is apt to advance with greater than normal rapidity, and to extend further than usual, so that the bone becomes denser and heavier than ordinarily.
The chief sign of rickets is the deformity which the soft and yielding nature of the bones occasions. As soon as the child begins to walk, the bones of the leg are unable to support the weight of the body, and so bend outwards. The pelvis, similarly, is crushed in by the weight of the backbone and its cavity nar rowed. This is specially serious in female children, for the pelvis retains its contracted form up to adult life, and so may obstruct or render impossible natural child-birth. The chest may be deformed, the sides drawn in and the front projected, forming the pigeon breast. On each side of the chest, a little to the side of the breast-bone, a mw of bead-like nodules is formed, the rosary. The bones of the head also partake of the disease, producing the peculiarly large head and protuberant forehead, while the face is small and peaked. In addi tion, the spine may also be curved, the joints are large and prominent, especially those of the wrist and ankle, causing the appearance called by some people "double-jointed," the growth over the whole body is generally stunted, so that the stature is small, the face is pale, and digestion imperfect. The child is often pot
bellied; the soft spot on the top of its head in front is larger, and later of closing, than usual ; and teething is delayed.
In its early stages the disease frequently re veals its onset by the restlessness of the child during the night, a tendency to kick off the bed-clothes, and profuse perspiration about the head, and a painful sensitiveness over the whole body, so that the child objects to be touched. About the age of fifteen the bones often be come quite firm, and a process of repair sets in, by which the hollows in the bones due to the bending may become filled up. Thereafter the excess of bone may be absorbed, and so the deformity become greatly diminished.
Treatment must supply defects in the diet, causing the disease, by substituting natural for artificial foodstuffs, especially fresh milk and eggs, by exercise, and by attention to the clothing to see that it is clean and warm, flannel being preferred. Change of air and sea-bathing are very valuable. As to drugs, the best are cod-liver oil and chemical food, given thrice daily in quantities to suit the age of the child, and iron, of which the most suit able form is dialysed iron, 5 to 10 drops four times daily in water.
To prevent the growing deformity of the legs various contrivances exist. The simplest is a wooden splint well padded and strapped on the outside of the leg from the thigh to the foot, which keeps the leg straight and strengthens it till it becomes able to bear the weight of the body. There are others, more complicated, made of steel fastened to the boot, and jointed at the knee so as to permit of bending. These are specially useful when the yielding is mainly at the joints, and not so much due to bending of the bones. There is now in use an operation for curing deformity due to the bending. It consists of cutting out a wedge-shaped portion of the bone, and then fixing up the limb, straight, as for fracture, and keeping it thus till the ends have completely united. It is em ployed only after the bones have become hard.