We have stated that the pus is seldom lau dable. On some few occasions, however, its consistence may be that of good pus ; but even then it soon degenerates into a thin fcetid sa nies of had quality. The openings giving exit to the discharge sometimes close very speedily, and new collections form in different parts of the tumour. This, however, is unfortunately rare, for generally the openings degenerate into fistulae. A probe introduced into one of these penetrates, if the route be not long and cir cuitous, into the interior of the joint, and dis covers the internal parts to be carious and dis organised; and if the bones of the articulation be now pressed together, a crepitation, arising from the friction of the carious and ulcerated surfaces, is perceived, furnishing unequivocal evidence of the last stage of disorganization of all the structures of the articulation. This is the most common course of the disease, but in some cases there are varieties to be observed. For example, the suppuration of the soft parts and of the cartilages, and even caries of the bones, may occasionally precede the displace ment of the bones ; and all the parts of the articulation may be destroyed without the oc currence of any displacement; but if, in this case, we move the bones of the articulation in opposite directions, we easily ascertain the re laxation of the uniting ligaments, and that many of the conditions necessary to the dis placement exist, although, from some cause not easily explained, it has not occurred.
As to our prognosis we should remember that the age and constitution of the patient have considerable influence on the ulterior pro gress of the disease, and our knowledge of this must control our anticipations as to the result to be expected, era eris paribus. The disease in the truly strumous subject is very rebellious, and has a disposition to terminate in suppu ration which it is difficult to baffle. In young subjects it is in general more acute, or the suc cession of the different orders of symptoms is more rapid ; but in young persons there is much more hope of cure than in the old and exhausted. We agree with Mr. Russell in opinion that it is in the cases of infants that the formation of anchylosis may be expected as the termination of a case of white swelling, though even with these true bony anchylosis must he considered as a very rare occurrence.
In the beginning the disease has but little influence on the constitution : it is not until it arrives at the second or third stage that it pro duces any very remarkable alteration in the health; but the pain about the commencement of the third stage is sometimes so violent as to deprive the patient of sleep and appetite. When the part is distended by abscesses, the pain is increased, but when these open or are opened, although temporary relief follows, slow fever supervenes, the discharge becomes sanious and foetid, and nocturnal sweats and colliquative diarrhoea skew themselves, together or alternately.
Anatomical characters of the chronic stru moia arthritis the knee.—The anatomical examination of a limb which has been ampu tated on account of a white swelling, or after the death of the patient, demonstrates different alterations which disease produces in the struc ture of the soft parts surrounding the diseased articulation, and in that of the bones, synovial membranes, and cartilages which compose it.
The skin and subcutaneous cellular tissue are not greatly altered from their natural condition, except that the latter is usually infiltrated with a gelatinous matter, as is also the cellular struc ture, which lies deeper, viz. that which unites the femur with the inferior part of the crurteus muscle, as well as that behind the ligament of the patella, and that also which occupies the intervals between the condyles of the femur behind the crucial ligaments. These parts are equally infiltrated by a gelatinous fluid, of more or less density. The whole of this cel lular structure presents the appearance of a soft, spongy, homogeneous mass. The liga ments which secure the junction of the bones of the joint seem themselves involved in this morbid change of the surrounding cellular structure, so that the tumefied ligaments and other structures seem to be confounded toge ther, and to present an appearance almost like a fibro-cartilaginous mass. " Thus have we seen," says Boyer,• " the fatty cellular tissue which is placed behind the ligamentum patella:, so dense and thickened that it formed but one mass in which ligament and cellular tissue seem confounded together." All these ap ces are present even before suppuration If the disease had existed for any length of time so as to have arrived at the period of suppuration, we find, among the structures thus altered, that symptomatic chro nic abscesses have been formed. One extre mity of them we observe usually communicat ing with the knee-joint, while the other reaches the surface, and presents one or more openings which had become fistulous. These abscesses and fistulous canals we find always lined by a false membrane. The muscles which surround the diseased joint are pale and wasted, and the cellular tissue which is found in their thickness is ordinarily more or less infiltrated with the peculiar glairy matter above alluded to. The tendons of the flexor muscles are generally re tracted and preserve their normal appearance. The nerves we have had occasion to observe to be thicker than natural. These are the altera tions which are noticed in the soft parts, as we pursue an anatomical examination down to the bones and ultimate structures of the joint it self. It is probable, however, that these changes will not be found to have occurred unless the disease has existed for some time previously in the centre of the bones them selves. Sir B. Brodie, Lloyd, and others are of opinion that this strumous disease begins in the centre of the heads of the bones of the knee-joint, in the cancellous structure ;• and Rust has satisfied himself that the membra nous tissue which lines the cancellous struc ture of the bones is the of the first morbid action. They have found the interior of the spongy tissue of the bones more vascular than natural, and with much apparent justice con ceive them to be inflamed. These changes, then, in the interior of the bone they believe to constitute the anatomical characters of the first period of the disease, and that when the parts external to the joint become swelled and infiltrated by the gelatinous matter above alluded to, the second period is fully established.