Immunity of Rats towards JenserbS Rat Sarcoma. 3 



(4) Cases in which the tumour spontaneously disappears ; these are 

 referred to as " Disappearing " tumours. 



The test as to whether a tumour belongs to type 1 or 2 is to make 

 frequent measurements of the superficial area of the tumour. If these areas 

 are raised to the power 3/2 and their logarithms when plotted are found to 

 lie on a straight line, then the rate of growth of the tumour has been 

 uniform ; a typical case may be seen in (1), fig. 1. No. 2 illustrates the 

 gradual diminution in the rate of growth which serves to distinguish type 2 

 from type 1. Nos. 3 and 4 illustrate the oscillating and disappearing 

 types respectively. 



The probability of success on re-inoculating animals which are bearing or 

 have borne tumours of any of the types specified may be gauged from the 

 data in Table I. » 



Table I. 



Character of 

 tumour. 



No. of 

 rats. 



Result of re-inoculation. 



Subsequent behaviour of tumour. 



Progressive 



Eetarded 



Oscillating 



Disappearing 



18 

 2 

 2 

 1 

 1 

 1 

 2 



1 

 1 

 1 

 3 

 2 

 3 

 1 

 1 



1 

 1 

 4 

 1 

 1 



1 

 8 

 5 

 1 

 21 



Graft took 



Grraft took but regressed 

 Grraft did not take 



Graft took 



Graft took but disappeared 

 Graft did not take 



)) >j ji 

 Graft did not take 



ij )) >j 

 Graft took 



Graft took 

 Graft did not take 



Graft took 



Graft did not take 



Progi'essed. 

 Retarded. 



Recun-ed after operation. 



Recurred after operation, then regressed. 



Retarded. 



Recurred after operation, then regressed. 

 Did not recur after operation. 



Progressed. 

 Retarded. 



Progressed, then retarded. 



Oscillatory. 



Retarded. 



Disappeared. 



Recurred but regressed. 



Did not recur after operation. 



Oscillated for six weeks, then progressed. 

 Oscillated. 



Gradually disappeared. 

 Oscillated. 



No recurrence after operation. 



Subsequently grew. 

 Disappeared. 



Did not recur after operation. 

 Subsequently disappeared. 



Judging from the behaviour of this strain of sarcoma in about 2000 inocu- 

 lations during the last four years, it is estimated that about 70 per cent, of 

 inoculations yield growing tumours of types 1 and 2, about 5 per cent, of an 

 oscillating nature, and 25 per cent, which spontaneously disappear. These 



