Tumor Growth. 



17 



Before the effects of tumor and other emulsions are described, it 

 is desirable to give the results of a control series of observations. 



Into 249 rats already having one tumor were implanted second 

 tumor fragments ; 59 per cent, of these rats developed a second 

 growing tumor. It was subsequently found that at the time of 

 the second implantations some of the tumors were already under- 

 going retrogression, and as the rats which have recovered spon- 

 taneously are more refractory than rats with growing tumors, this 

 percentage of successful secondary transplantations should prop- 

 erly be stated still higher. 



Into each of 70 rats which had recovered spontaneously from 

 growing tumors, a second implantation of tumor particles was 

 made ; 17 per cent, of these were successful. 



Into 201 rats which had been inoculated once unsuccessfully 

 with the tumor while its virulence was below the maximum, second 

 implantations of the virulent tumor were made ; 49 per cent, were 

 successful. 



With this series is to be compared the next to be given. 



A group of rats in which the tumors were being absorbed or 

 were entirely stationary was divided into halves. One half was 

 injected with heated emulsion and ten days later with tumor. 

 The tumor grafts grew in 60 per cent, of these animals. The 

 other half received the tumor but no emulsion ; the grafts grew in 

 36 per cent. The control series gave 100 per cent. 



Taking a second group of rats in which the growing tumor was 

 later absorbed, the same experiment was carried out. The rats 

 not receiving the heated emulsion developed tumors in 9 per cent., 

 while those receiving the emulsion developed tumors in 30 per cent. 



We now return to a group of rats which having been injected 

 with the heated emulsion and successfully inoculated with tumor 

 subsequently recovered. A second injection of heated emulsion 

 was given to one part and none to another. At the expiration of 

 the ten day period, new tumor grafts were implanted with the effect 

 of producing 30 per cent, of tumors in both series. Here again 

 the control rats gave 100 per cent, of tumors. Hence it appears 

 that no such discrepancy in promoting effects arises from a second 

 as from a first injection of the heated emulsion. But what is 

 equally surprising is the high percentage of successful secondary 



