Acute abscesses, as indicated in the previous chapter, have no real limiting membrane, although there is more or less condensation of tissues about the focus of infection. A typical membrane is distinctive of tuberculous abscesses, and is to be regarded always as their natural protection and a barrier against their further encroachment--a membrane whose inner surface may harbor active organisms which cannot escape through its outer texture. Consequently, to simply incise it or inefficiently scrape it is to do a worse than useless thing; and one should never attack it unless he is prepared to extirpate it or destroy its integrity, and in this way dispose of it. Cold abscesses when near the surface cause a bluish or dusky discoloration of the overlying skin, while the superficial and subcutaneous veins of this region are usually enlarged. Fluctuation is also a prominent phenomena in connection with them when they can be palpated. Deep collections of this kind may be mistaken for cysts or tumors, in which case the aspirator needle may be used to facilitate diagnosis. They vary in size from the smallest possible collection of fluid to abscesses which may contain a gallon or more of puruloid material or archepyon. They are known often as _gravitation abscesses_, because by the weight of the contained fluid they tend to elongate or spread themselves in the direction in which gravity would naturally carry a collection of fluid. Thus cold abscesses originating from tuberculous disease of the lower spine frequently work their way along the psoas muscle and present below Poupart’s ligament as _psoas abscesses_, or elsewhere about the thigh, while those which come from similar disease of the uppermost cervical vertebrae may present behind the pharynx, as the so-called _retropharyngeal abscesses_, and those from the dorsal spine present not infrequently as _lumbar abscesses_. These are but two or three familiar examples of what may occur in any part of the body. =Treatment.=--Aside from the treatment of cold abscesses, already indicated by radical measures, other means have been suggested, and particularly for the treatment of those in which such extreme measures are impracticable or impossible. It is sometimes efficacious to simply tap or remove by aspiration the contents of such a cavity. It may never refill, or but slowly, and after repeated tapping alone a very small percentage of such cases will subside into inactivity and the lesion be subdued, if not absolutely cured. Treatment by injection of emulsions of iodoform has found favor with many surgeons. I have never been able to secure the good results reported by others, and consequently have abandoned it; yet it deserves mention here because of the repute it has enjoyed.