This disease has been supposed to commence in the cartilages; it appears, however, to originate indiscriminately in the cartilage and the bone, as well as in the membrane lining the capsule and investing the cartilage and the ligaments; but whether it begins in one or other of these tissues, it soon, if neglected, involves them all. It affects patients of all ages, though children under twelve are most generally its victims; and in these it often makes considerable progress without its existence being suspected. The patient is observed to be a little lame, and to be awkward in the use of the affected limb, but he experiences little or no pain in the first instance; and if he does, it is of a dull kind, and generally referred to other parts. Thus, pain in the knee is generally the prominent symptom of this affection, and occasionally pain is also referred to the ankle, or to the sole of the foot: careful study and considerable experience are here required, to guard the young practitioner from error in diagnosis. Parts remote from the seat of morbid action have often been made the subject of treatment in this and other affections; the knee, in morbus coxarius, has been leeched, poulticed, blistered, and burnt, and that, too, when this joint was not at all altered in appearance, and showed no symptom of disease. Again, and particularly in adults, the limb is easy only in certain positions, and cannot be moved without great suffering; pain is also complained of in the groin, and often immediately behind the trochanter major. If an examination is made when the patient is thus halting, and even though he complains of no pain, the limb is found shrunk, wasted, and lengthened. The elongation of the limb occurs mainly in consequence of the inclination of the pelvis towards that side. When the disease has made progress, it has been supposed that swelling of the apparatus of the joint, and effusion into its cavity, might separate the head of the bone from the acetabulum, when pressure from the trunk was not applied. The lengthening is often great, and its extent and cause are ascertained by accurate comparison of the two limbs, laid in contact when the patient is in the recumbent posture. [Illustration] The degree of lengthening is here carefully represented from a recent case. But occasionally, even in the first stage, before destructive ulceration has set in, in consequence of the pain and spasms, the limb becomes remarkably shortened and retracted. This also will be found, on careful examination, to depend upon the relative positions of the two ossa innominata.