In some cases the diagnosis cannot be determined accurately until after one or more teeth are removed that are involved with the tumor. After such operation, a probe carried through the alveolus will usually reveal the true condition of the lesion. One or more dead teeth are found involved--one, however, being the rule in most cases which have come to the notice of the writer, while two, and sometimes three, are implicated with the tumor. The dead tooth may be easily distinguished from the living ones by its opaque appearance. Such tooth may be carious, and it may not. Primarily the dentritic cyst originates from what pathologists call a "cold abscess," that is, an abscess which has never opened; subsequently, having developed into a tumor. The interior of the cyst has a fibrous lining, and being compact in structure, is the seat of an inflammatory process. The cyst contains a pyriform fluid; it may attain such magnitude as to invest several teeth and extend beyond the alveolar process. The tumor is usually oval in shape, with its apex on a line with the diseased tooth directly involved. The size of the tumor may be as large as a hulled walnut or as small as hazel-nut; crepitates under pressure, and feels like parchment. In cases of long standing, considerable resorption of the alveolar process takes place, and the teeth immediately connected will be loose; especially will this be the case if the alveolar borders are broken; these teeth should be removed. These tumors are found painless, as a rule. I have met with cases, however, where an acute inflammatory condition was present, with all the symptoms of acute periodontitis manifested. So that it could have been readily mistaken for the pointing of an alveolar abscess. _Pathology._--Cysts of the jaw may be either simple or compound; whether they be cysts of retention, exudation cysts, or extravasation cysts belonging to the jaws, is a matter not as yet fully established. The exudation cyst is a secretory cyst; in a generic relation, however, it is just the opposite of the retention cyst. Serous sacs form the foundations of the exudation cysts. "The mode of development of cysts of the jaws," says Wedl, "has not yet been determined; it therefore becomes necessary, in order to throw more light on the subject, to pursue further anatomical investigations in that direction."