up partly of bony plates and partly of fibrous FIG. 1. Before operation. I tissue, the interior being lined by a smooth, shiny membrane I somewhat resembling h e mucous membrane of the mouth. This large cyst communicated with other cysts, and across its FIG. 2. ._tr= optfratioll. cavity stretched fibrous bands, evidently the remains of a partition between it and some other cyst. The contents of the larger cysts resembled chocolate in colour and consistency, but in the smaller ones the fluid was

more »

... clear and mucoid. The coronoid process of the jaw was hollowed out right up to its tip and the condyle was involved as far as the neck, so that it stood out like a button from the growth. The cut surface near the symphysis clearly showed that the growth originated in the central or cancellous portion of the jaw, distending the outer compact wall, and here was also some solid material which had not yet become cystic. The three teeth in the part removed were in the roof of a large cyst. On making sections of a small cyst which had thrown out a process I found that the cyst consisted of a wall of fibrous lamellas lined on the inside by columnar epithelium. In the process of the cyst was more solid matter, and here I found masses of epithelial cells breaking down in the centre and forming cysts. In cysts of the size of a hazel-nut I found traces of epithelial lining, but in the largest cysts this had disappeared altogether. On the outside of the jaw near the teetn 1inere was a soua portion or Tissue wmcn was maae up of epithelium becoming cystic. An examination of the gum over the tumour showed that it was fairly normal, but at one point the epithelium showed signs of growing in. The tumour was therefore a multilocular cystic epithelial tumpur. After the gouging operation which I did on this case in 1897 I could find no traces of epithelium in the parts removed, but I had not at that time any of the solid portion of the tumour from the margin of the growth and I therefore drew erroneous conclusions concerning its nature. It was not until the growth had broken through the bony wall of the jaw that the increase in size took place. The tumour then became painful from pressure on surrounding parts setting up severe neuralgia ; there was also some pressure on the pharynx and difficulty in taking food. As the tumour had lasted 20 years some idea of the slowness of its growth may be gained. I could get no history of tooth irritation at the commencement of the disease. The microscopical sections show every stage from the mass of epithelial cells to the fully developed cyst. Liverpool.