206 



Dr. Russell. The Manifestation of Active [Mar. 15, 



then testing the suitability of the animals for re-inoculation. It was found 

 that, in about 60 per cent, of the cases, strain 199 had rendered the animals 

 resistant to re-inoculation, a result which conforms with that previously 

 obtained. 



This concludes the description of the findings with mouse tumours, which 

 indicates how extremely variable in action their parenchymata may be, leading 

 from the case where no resistance is induced, through all gradations to the 

 case where resistance is induced in every animal. 



The behaviour of a transplantable rat sarcoma, obtained from Jensen, 

 has also been investigated in a manner similar to those already 

 detailed for various mouse tumours. This strain, J.E.S., is a rapidly 

 growing spindle cell sarcoma which gives a high percentage of success on 

 transplantation. 



Spontaneous healing occurs with great frequency in series of this tumour, 

 and large masses of growth, weighing 10-15 grm., often disappear entirely. 

 The re-inoeulability of rats bearing this tumour has been already described 

 and figured* and it was then concluded that the results obtained on 

 re-inoculation could be explained only by assuming the development of 

 resistance during the growth of the tumour first inoculated. The presence 

 of large rapidly growing neoplasms during the period in which the re-inocula- 

 tion tumours are developing, presents both an actual and a theoretical 

 complication which it seemed desirable to eliminate. Accordingly the tumours 

 from the first inoculation have been allowed to develop for a certain period, 

 then all have been excised, and a re-inoculation has been made to ascertain 

 what alteration had taken place in the suitability of the soil. 



In one experiment conducted with this rat sarcoma, the result of 

 re-inoculating seven rats, whose tumours had been completely extirpated, 

 was that in only one animal was a tumour obtained approximating those of 

 the control series in the speed of its growth. In two cases the re-inoculation 

 was entirely negative, whilst in the remaining four only small nodules 

 developed. In six of the seven animals there was thus a considerable 

 degree of resistance developed from the tumour first inoculated. In seven 

 other rats from the same series the excision was intentionally incomplete, 

 but the result of re-inoculation was practically the same as in the rats 

 where the excision was complete. These findings do not harmonise with 

 those of Uhlenhuth, Haendel, and Steffenhagen,f who found that incomplete 

 excision left the animals suitable for re-inoculation. In the above series of 



* Loc. ait., p. 203. 



t Uhlenhuth, Haendel, und Steffenhagen, " Experimentelle Untersuchungen iiber 

 Eattensarkom," 'Arb. a. d. kais. Gesundheitsamt,' 1911, vol. 36, p. 465. 



