2 Mr. J. C. Mottram and Dr. S. Russ. Susceptibility and 



Part I. — Conditions of Susceptibility and Immunity. 



1. The Condition of Susceptibility. 



The Jensen's rat sarcoma used in this investigation was kindly provided , 

 by the Imperial Cancer Eesearch Fund, and has been in continual propaga- 

 tion in this laboratory during the past five years. 



The inoculation of normal rats with this sarcoma results in the large 

 majority of cases in a growing tumour. The behaviour of the tumour has 

 been investigated in detail. 



Four types of growth are clearly distinguishable ; they are : — 



(1) Cases in which the rate of growth of the tumour is uniform ; these are 

 referred to as " Progressive " tumours. 



(2) Cases in which the rate of growth gradually diminishes as the tumour 

 increases in size ; these are referred to as " Eetarded " tumours. 



(3) Cases in which, after attaining a certain size, the tumour oscillates 

 between narrow limits for long periods of time (often for months) ; these are 

 referred to as " Oscillating " tumours. 



Fig. 1. 



