A node is a swelling situated over a bone, hard, firm, and exquisitely tender to the touch, not round or circumscribed at its base, but gradually subsiding to the level of the adjacent parts, and not discoloured on the surface. It is at all times painful (except in some scrofulous cases), and when arisincg from a venereal cause, is subject to nocturnal exacerbations of great severity. The morbid anatomy of the disease is not always the same even when examined at the same period of duration, being modified by a number of circumstances, such as the age of the subject and consequent vascularity of the bones; the structure of the bone en gaged being solid and firm or soft and spongy ; but more particularly by the fact of the disease being idiopathic, or produced by some consti tutional affection. The scrofulous diseases of bones seldom or never exhibit the symptom of nodes, although attended by suppuration, be cause they affect their substance rather than their surfaces : idiopathic nodes, or those pro duced by injury, do not suppurate unless the violence used is great; on the contrary, these are cases which so frequently terminate in thickening of the periosteum, &c., and often, when cut into, scarcely afford any perceptible discharge. The venereal or mercurial node offers the best example of suppuration. At an early period, if an opportunity occurs for exa mination, the periosteum round the margin of the effusion shews a more than ordinary degree of vascularity ; immediately covering the tu mour it is somewhat paler, more opaque and thickened. The bone underneath is denuded and soon runs into caries ; between it and the membrane the matter is deposited, thin in con sistence, dark-coloured, and sanious.
There are other forms of suppuration on the, surface of a bone of too much interest and im portance to be omitted, such as those large de pots which occasionally occur after severe in juries or operations as the accompaniments of inflammation of the veins, or as the sequeloe of acute fevers. In general, the matter is in great quantity and of a good and healthy cha racter, though sometimes it is otherwise, and particularly in that form which attacks a stump after amputation. We have seen the entire remnant of the bone up to the next articulation denuded of its periosteum, while quantities of green and fetid pus could be pressed from the very depths of the wound. In these cases the veins are generally inflamed, the divided ends of the muscles pale, flaccid, and sloughy, and the patient seldom or never recovers. Where the deposition has taken place after fever, if the patient is young and the constitution has enabled him to combat the original disease, a recovery very frequently takes place by the process of necrosis.
Caries from a scrofulous cause, generally, if not always, commences in the cancellated structure ; that from syphilis affects the firmer and more external parts of the bone. The former attacks the ends of the long bones and the spongy and cuboid bones generally ; the latter, the centres of the long bones and the flat ones. Venereal nodes principally affect the bones which are nearest to the surface of the body, the skull, the tibia, or the sternum ; it being rare to see the humerus or femur thus diseased, whilst they are by no means exempt from idiopathic or strumous inflammation. But the inost remarkable differences to be ob served between caries arising from a specific cause, and that which occurs idiupathically or from injury in a constitution otherwise good, occur in the progress and termination of the disease. The process seems to be analogous
to that of ulceration in the softer tissues, and when recovery takes place, it is by granulation and cicatrization in like manner. Thus, if we suppose an abscess to occur on the surface of a bone in a healthy man, when it is opened or has burst, we find that a scale or shell has lost its vitality and must be thrown off by exfo liation, and soon exuberant and florid granula tions are seen spring,ing froin below as if to force the offending substance off, and the dis charge from the cavity is healthy pus. On the other hand, if a venereal node is opened on the skull, the pericranium is here detached, the table is carious and will exfoliate, but there is (as long as the taint remains) no effort a.t re .paration ; the discharge is thin, ichorous, and unhealthy ; and if we may judge by the repre sentations we see of venereal caries, (for in modern times mercury is not so unsparingly used and real specimens are not numerous,) the disease would progress until the skull was fairly corroded through. Again, the lymph secreted in scrofulous inflammation is not healthy, and there are seldom granulations; whilst the matter is either of that whey-like appearance so remarkable in such affections, or else a foul and fetid sanies. Every one con versant with surgery must know how tedious and obstinate a scrofulous caries is, and how frequently it involves the loss of limb or of life.
The true scrofulous affection of the bones occurs so frequently in this country as to re quire particular attention ; it constitutes the vast majority of the diseases of the osseous system that we are called upon to see and to treat. It commences (as we have said) in the cellular or cancellated structure. In the first instance there is an increase of vascularity, which, though not always apparent to the eye, may easily be proved by injection. Next, there is an absorption of' the natural contents of the cancelli, and in their room a substance is deposited of a yellow or white colour that has been described as resembling cheese in consistence ; it is, however, most probably a species of that flocculent unorganized lymph, such as is seen coating the cysts of scrofulous abscesses. The utricelli themselves are oc casionally removed, and masses or patches of this unorganized material deposited in their stead, hence the bone becomes lighter, and so soft as to allow of being cut with a knife. It is remarkable that the disease may have existed up to this period, when it is probably incura ble, without much pain and without external swelling to attract attention to the mischief underneath. In the Museum of the School of Anatomy, 8.cc. of Park-street, Dublin, there is a preparation to illustrate necrosis of the centre of the shaft of the thigh-bone, for which the limb was amputated. The patient during life never. complained of the knee, neither was there the smallest enlargement of the articula tion ; yet after removal the condyles of the fernur internally were completely softened, the external shell of solid bone being reduced in thickness nearly to that of parchment, the can cellated structure completely removed, and its place occupied by this cheesy substance.