Cytological Studies on Cancer, VI. Spontr.tneous Tumors occurring in Inbred Mice, with Notes on the Establish- ment of Two New Strains of Transplantable Tumor l) By

The transplantable nature of cancer is one of the most interesting and important problems in cancer research but it is left not fruitfully interpreted at present. Research by means of transplantation of the tumor spontaneously caused to occur is one of the avenues to approach its elueidatior:. Thus scyeral investiga-tions have been made along this line from both histological and pathological stand-points. Since 1944, the author has engaged in inbreeding experiments of mice with the support and direction of Professor:Makino, in order to establish pure strains. During the course of the work the author has had several opportunities to meet with the occurrence of spontaneous tumors in mice of a certain strain which had been established and purely bred in this laboratory. This paper deals with the histological characters of these spontaneons tumors and their transplantability, with some notes on two strains of transplantable tumors newly established. Here, the author would express his gratitude to Professor Sajiro Makino for his valuable advice ancl for goinG through tll " mannscript. Further thanks must be extended to Professor Katsuo Takeda of the Pathological Institute of the Medical Faculty for his important criticism. 1. Strains oJ tumor mice aud methods of transplantation The number of indi',idu<ll mice in which tumors havE ' c18vrloped \';as 11 in total; they are derivati\'es from three strains called D, B and So. They may b