304 Drs. Bashford and Russell. Homogeneity of [Jan. 17, 



with a small central canal containing the inoculated tumour tissue, for the 

 most part as necrotic d6bris. If examined at an earlier date, fifth or sixth 

 day, small islets of carcinomatous tissue are seen lying in a very cellular 

 tissue, the whole having tlie appearance almost of a carcinoma-sarcomatodes. 

 If the tumour be removed from the rat at this earlier stage, and inoculated 

 back into mice, it gives rise to tumours, but these do not grow so well as 

 before passage through the rat, and the percentage of tumours obtained is 

 only about a third of the previous percentage. 



Nine rats, weighing 490 grammes, were inoculated on the dorsum with 

 0'2 c.c. of an emulsion of mouse tumour " 199." Three days later, other nine 

 rats, weighing 510 grammes, were inoculated in exactly the sanae way witli 

 the same tumour ; and again, three days later, a third batch of nine rats, 

 weighing 540 grammes, were treated with the same tumour in the same 

 manner. Three days after inoculation of the last batch, that is nine, six, and 

 three days respectively, after the primary inoculation, these three batches of 

 rats were tested simultaneously by inoculating " early stages " of anotlier 

 mouse tumour in the right axilla. Twelve normal rats, weighing 

 455 grammes, were also inoculated with early stages to serve as control. 

 These early stages were removed at 24, 48, 72 hours after inoculatidn, and 

 examined in serial sections. In the normal control rats the " early stages " 

 continued to grow for the first three days. The tumour cells continued to 

 divide, whilst the introduced stroma degenerated, and was beginning to ])e 

 replaced by a fresh stroma from tlie rat tissues on the third day. In the 

 batch of rats treated three days previously with 0'2 c.c. of mouse tumour, no 

 difJ'erence could be seen in the early stages as compared with the control 

 early stages in normal rats. There was no marked difference, also, in the 

 case of the batch treated six days previous to inoculation of the early stages. 

 In the batch of rats which had been treated nine days previous to testing 

 with " early stages," quite a different state of affairs obtainetl. In the grafts 

 examined after 24 hours' residence, a large number of the introduced tumour 

 cells, botii in the peripheral and central parts of the graft, had been killed. 

 Further, there was a complete absence of mitoses of the tumour cells. 

 Mit(jtic division of the adjacent connective tissue cells of tlie rat was already 

 ])n!sont, and there was a large exudate of polymorphonuclear leucocytes. At 

 4(S liours only a f(;w tumour cells, mostly in the central of the graft, had 



letaiiied tlirir morphological characters. By 72 hours, all the tumour cells 

 had Iteen killed oil', and an abundant reaction tissue was being formed by tlie 

 rat tissues. 



Such ('XpeiiiH(!iitH denioiiHtrate in the clearest manner that after inocu- 

 latinn of a given dose of mouse tumour into a rat, there is produced between 



