Fluctuation, usually detected with ease, is sometimes hidden by a thick investing layer of lymph, which gives the mass a peculiar tension, suggesting a lipoma or some other hard growth. Aneurisms sometimes convey the sensa tion produced by a cold abscess: a fact to be borne in mind when operative pro cedures are under consideration.
Pathology. — A cold abscess can al ways be traced to a specific inflammatory process, and almost invariably to one of a tubercular nature. Where the conflu ent masses in the centre of a nodule begin to break down, there is formed a collection of material surrounded by tuberculous tissue. This material be comes infiltrated with lencocytes, and thus is produced a cavity containing fluid fatty material, fragments of cells, and leucocytes, around which there is granulation tissue filled with tubercles. In this way a tuberculous abscess is formed. (Cheyne.) It seems at times to be quite a matter of accident whether the abscess breaks into the joint or finds its way by a more circuitous route into the surrounding connective tissue. As the tuberculous masses spread, caseation takes place at different points in the wall, and the masses are discharged into the cavity of the abscess; but the spread of the abscess is effected generally by what is termed "burrowing of pus." This burrowing occurs in various direc tions. and large collections of pus, alto out of proportion to the original lesion, are formed, and are known as cold abscesses. (Warren.) What has been called a chronic ab scess is very often no abscess at all. In tubercular J processes the product of tissue-proliferation undergoes coagula tion-necrosis, and disintegrates into a granular mass, which, when mixed with a sufficient quantity of serum, forms an emulsion that microscopically resembles pus, but under the microscope shows none of the histological elements which are found in true pus. An abscess can only be called such if it contain pus. A true chronic abscess can originate in a tubercular, actinomycotic, or syphilitic lesion, when the granulation tissue is secondarily infected by the localization of pus-microbes, which convert the em bryonal cells into pus-corpuscles. (Senn.) Differential Diagnosis.—The concom itant disorder usually makes a diagno sis easy in a case of cold abscess; but occasionally the swelling is the only in dication of ill health, and it is important to determine, under such circumstances, the nature of the pus. The macroscop
ical appearances of "laudable" pus and of "sanious" pus are frequently so simi lar that a de visu diagnosis is not justi fied. Bacteriological examination of the contents of such abscesses will show con clusively whether they are true pus-con taining abscesses or whether or not they are pseudo-abscesses. If cultivations are made of their contents, pus-microbes will grow upon proper nutrient media if it be a true abscess, while, from the con tents of a pseudo-abscess only the mi crobes of the primary infection can be cultivated. The information obtained by the discovery of the essential cause can be confirmed by inoculation experi ments. (Scum.) Prognosis. — The walls of cold ab sccsses are usually tense and tough, and are lined with cheesy tuberculous ma terial. They do not tend to collapse, as is the case with acute abscesses, and for that reason are healed with difficulty. When, however, the seat of the original trouble call be reached and successfully treated. the fluid in the parts of the ab scess-tract is absorbed, and the easeous matter undergoes calcification. This fortunate issue of the case is seldom met with, however, and the abscess usually continues, the primary etiological factor acting as a drain for the diseased area. The prognosis, therefore, depends upon the result obtained in the treatment of the latter.
Treatment.—It is a well-known clin ical fact that, when such a cold or tuber culous abscess opens spontaneously, or is incised in a careless way, profuse sup puration and hectic fever follow, with only too often a speedy fatal result from septic infection. Unless the surround ings of the patient admit of carrying out the antiseptic treatment to its full and perfect extent, a chronic abscess should not be evacuated by incision. It should be aspirated. When an incision can be made, it should be free, and the cavity should be thoroughly curetted, cleansed,, disinfected, and iodoformized, then su tured, drained, and treated as a recent. wound.