204 



90 . 



Dr. Bashford and Messrs. Murray and Bowen. [May 30, 



Fig. 2. — Graphic record of steps by which, starting from a tumour giving 15 per cent, of 

 success on transplantation, 40 I, a tumour was obtained after eight subse- 

 quent transplantations, giving 84 per cent, of success, 48 E. The success on 

 transplanting some of the other tumours propagated at each step is also 

 recorded by the points at the ends of the lines branching off from the " main 

 stem " of propagation. 



When the curve has reached a maximum it falls rapidly in marked 

 contrast to the preceding gradual rise. The seven tumours of 48 E do not 

 all fall to the same level; the degree of the diminution in the success 

 attending subinoculation varies, but the direction of the curve is downwards 

 in all. This sequence of a gradual rise in transplantability followed by a 

 fall has been repeatedly observed during the past two and a-half years. 

 Although in this particular case the fall in percentage of success on trans- 

 planting tumours of 48 E is rapid, and attains a minimum at the first essay 

 with many other strains, it has been possible to obtain several estimations on 

 the downward slope of the curve. In such cases, when the tumours of a 

 series following on a maximum are again transplanted, a further diminution 

 in the percentage of success is frequent, if the diminution in trans- 

 plantability had been slight in the first instance. The accompanying chart 

 (fig. 3) illustrates these points very clearly. It represents the results 

 obtained by transplanting a large proportion of all the tumours of another 

 series, viz., 50 Z, which had indicated 90 per cent. -of transplantability. The 

 daughter tumours of this series giving rise to 51 U and 51 T, showed the 

 smallest diminution as compared with 50 Z. From each several tumours 

 have been transplanted, and in each case the diminution in the percentage of 



