It is in the diagnosis of obscure pathologic conditions that the physician of unusual ability is distinguished from the ordinary physician. Among such conditions may certainly be mentioned the dermoid cysts and teratomas of the anterior mediastinum. Dangschat,1 an assistant in Garré's clinic in Königsberg, gives practically all the information obtainable on this subject up to this date. He reports two cases operated on in the Königsberg clinic and has collected from the literature forty-four similar, cases. Only two of these are from American journals, one reported in 1879, and three others are mentioned from English sources.
Various theories have been advanced to account for the origin of these tumors. The origin by direct embryonic inclusion, by development from the thyroid or thymus or from the gill-slits, Dangschat rejects on the basis of careful examination of the material obtained at operation in these cases. The new growth contains tissue