An adult, in a case where no violence hath been committed or received, usually complains first of weakness in his back bone, accompanied with a heavy dull pain, and great lassitude: this is soon followed by an unusual sense of coldness in his thighs, independent of the weather or any obvious cause: his limbs are soon afterwards affected with an unusual sensibility, and frequently convulsed by slight spasms, particularly troublesome in the night. Soon after this, he not only becomes incapable of walking, but his power of retaining or discharging his urine or faeces is considerably impaired. The adult, as well as the child, complains constantly of a tightness and pain at his stomach, and he finds all the offices of his digestive and respiratory organs much impaired.

The loss of motion in the limbs, which generally accompanies a distorted spine, proceeds from this distortion. Until the curvature is discovered, the complaint is considered as nervous; but when the state of the vertebrae is known, it is attributed to some previous blow, fall, or other accident. In some few instances these may have produced the effect; but, in the majority, some predisposing cause, in which the very essence of the disease consists, may be found; and this is a distempered state, generally an inflammation of the ligaments and bones, where the curve soon after makes its appearance. This occasions the ill health of the patient, and in time the curvature. The helpless state of the limbs is the consequence only.

It has been supposed that there is a dislocation of the vertebrae; but the spine bends forward only because the diseased bones, intervening between the sound ones, are unable to bear the parts above. From every circumstance it is evident, that the complaint arises from a scrofulous indisposition affecting the parts that compose the spine, or those in its immediate vicinity: this morbid affection shows itself in a variety of forms; but they, in every instance, determine the true nature of the distemper. Sometimes the deformity of the spine occurs, without any apparent disease of the bones composing it; sometimes the deformity is attended with erosion, or caries of the body of one of the vertebrae; and the same bones are occasionally found to be carious, without any crookedness or alteration of figure. Strumous tubercles in the lungs, and a distempered state of some of the abdominal viscera, are often attendants of this complaint.

When these complaints are not attended with an alteration of the figure of the back bone, neither the real seat nor true nature of the distemper is pointed out by the general symptoms, and they are frequently unknown while the patient lives. When the ligaments and cartilages of the spine become the seat of the disorder, without any affection of the vertebrae, the whole spine, from the lowest vertebra of the neck downwards, gives way laterally, forming a great curve on one side, sometimes a more irregular figure, attended with many marks of ill health. The attack is occasionally on the bodies of some of the vertebrae; and ulceration, with erosion of the bones, is the consequence. This erosion of the bones often produces the curvature peculiar to the disease, by wasting the body of each vertebra affected; and then the spinal processes of the diseased vertebrae protuberate behind, in consequence of the decay of their fore parts. When the dorsal vertebrae are attacked, the sternum and ribs, for want of proper support, necessarily give way, and additional deformity is produced. It sometimes happens that internal abscesses and collections of matter are formed near the spine, which, affecting the spine with caries, and proceeding outward, produce what is called a psoas abscess, and destroy the patient.

If we carefully examine this disease, it will be found, as we have said, to originate from a scrofulous habit, perhaps from a disease of the ligaments, and particularly inflammation of the vertebrae themselves. What we style inflammation of the bones, differs from that of the softer parts. It is rather a slight increased action of the vessels, soon destroying their vital principle, probably from pressure, as distention is not admissible. The bones, thus partially destroyed, are pressed on unequally, and deformity necessarily ensues. When the outside of the vertebra is decayed, there is little change; for the flexors of the trunk are strong, and a slight stooping soon relieves the diseased part. When decayed within, to preserve the equilibrium, the neighbouring vertebrae, start out. When the disease is on either side, the curvature is on the opposite, but the curvature on the side is seldom alone. To prevent uneasiness, the patient reclines to the opposite side, and this produces the counter curvature, formerly described.

It will be obvious that the nerves coming from the diseased bone will be compressed by the curvature; but this compression is not complete, and, like all imperfect compressions, is attended with irritation. Thus the early compression in hydrocephalus appears with all the marks of irritation. This is the reason why the paralysis, from curved spine, is attended with spasms, and differs, as we shall soon mention, in this essential circumstance, from other paralyses.

There is another circumstance of some importance, which we must add. If from tonics, or any general plan of restoring strength, the general health is amended, whatever remedy is directed to the spine, the disease is relieved, and often when no application is made. This, though not an isolated fact in nervous compressions, is yet difficult of explanation. It may arise from anastomosis of nerves; but we know not that nervous influence is retrograde or lateral. We suspect, therefore, that the nervous energy, like the arterial, is increased when any obstacle has been interposed; and by this increase the functions are, at least in some degree, restored.

Mr. Pott observes, that, in compliance with custom, he hath called this disease a palsy; but that, notwithstanding the limbs be rendered almost totally useless, yet there are some essential circumstances in which this affection differs from a nervous palsy: the legs and thighs are rendered unfit for all the purposes of loco-motion, and have lost much of their natural sensibility; but they have not the flabby feel of a truly paralytic limb, that seeming looseness at the joints, nor that total incapacity of resistance which admits of motion in almost all directions: on the contrary, the joints have frequently a considerable degree of stiffness, particularly the ankles, so that the feet of children are generally pointed downwards; and they are prevented from setting them fiat on. the ground: the legs of the patient are either constantly kept stretched out, and considerable force is required to bend the knees, or they are by the action of the stronger muscles drawn across each other, and require as much to separate them. When the leg is in a straight position, the extensor muscles a< 1 so powerfully as to require a considerable degree of force to bend the joints of the knees; and when they have been bent, the legs arc immediately and strongly drawn up, with the heels towards the buttocks; by the rigidity of the ankle bones, added to the spasmodic action of the gastrocnemii muscles, the patient's toes are pointed, as we have said, downwards in such a manner as to render it impossible for him to put his feet flat on the ground; which makes one of the decisive characters of this distemper. Thus the marks of distinction between this disease and the palsy are sufficiently strong to show the impropriety of confounding them, and from the slightest attention the two diseases may be easily distinguished.