DURING the course of t h e experimental propagation of turnonrs in auiiuals, it occasionally happens t h a t i n the stroma surrounding a carcinoma a sarcoma may develop. This process has been very caiefully worked out in mice by Haaland (190S2), and again by Russell (1 9 1 03). Askanazy (1 9 0 9') obtained a sarcoina i n a white rat, in a snbcutaneous teratorna which had grown for two years. I n this case the teratoma had been produced by inoculation with a n emulsion of rat f e t u s . As,

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... herto, t h e development of a n epithelial turnour i n association with a transplanted sarcoma has not been observed, the following case is sufiiciently interesting to be published. A fully grown young female white rat (exact age unknown) was inoculated under the skin of the right flank with a portion of a sarcoma which had originally been given to us by Dr. Bashford. A tunlour debeloped close to the site of inoculation; in six weeks this measured 18 by 1.5 mm. in its two longest diameters. During the seventh week it diminished in biee to 13 by 9 mm. The rat mas then killed, and the complete tumour, together with the overlying skin and the surrounding connective tissue, was cut in serial sections. At the autopsy no other tumour was found, and, to the naked eye, all the organs were healthy. The specimen was so imbedded that it was cut along its smallest diameter. The thickness of the sections was 10 p. I\IICROSCOPIC ~XAMIxATIoN.-Considerable shrinkage has taken place. The whole of the graft of sarcoma has died and its place has been taken by necrotic material which consists of sarcoma cells and leucocytes. This mass lies in a cavity from the walls of which it has shrunk (cf. Fig. 1 , in which the cavity alone is shown). Near one end of the series, the skin over this necrotic tumour has given way, and the latter has thus become liable to infection from without. The cavity is surrounded, everywhere, by a mass of young granulation tissue, with a layer of fibrin covering it in many places. It is necessary to say a few words about the area where the qkin has given way over the graft. This occurs near one end of the series. The perforation is exceedingly minute, so small that it was not noticed with the naked eye. The edges of the skin are turned in and the epithelium has qrown along the wall of the cavity, in every direction, for a very shalt