Immunity of Rats towards Jensen's Rat Sarcoma. 9 



progressive tumours were positive to a fresh inoculation, and that in some 

 of these cases a considerable increase in their leucocyte and plasma-cell 

 content occurred ; in other animals which were resistant to a re-inoculation, 

 although bearing progressive tumours, there was no appreciable increase in 

 the lymphocyte and plasma-cell content directly associated with the appear- 

 ance of the immune condition. 



The outstanding features of the investigation are : — 



(1) The lymphocyte and plasma-cell content of normal rats varies within 

 wide limits, but the number having a low content is very much larger than 

 the number having a high content [vide diagram (N)]. 



(2) The immune animal is just about as likely to have a low as a high 

 content (I) ; " Massive " immunes (vide fig. 7) are almost always packed 

 with cells of the kind considered (M). 



(3) There is about an equal chance in animals which bear either a 

 progressive or a disappearing tumour, having a high or low cell content 



in (D). 



Any observed increase in the lymphocyte and plasma-cell content is not 

 due to intolerance of the spleen to repeated interference with it — this was 

 shown by separate tests upon normal rats. Neither can the variations be 

 induced by inoculating dead cells into the animals ; this was tested by 

 inoculating boiled sarcoma cells with two subsequent examinations of the 

 spleen content — no appreciable variation of the lymphocyte and plasma-cell 

 content occurred. 



Tumours in Living Hat Tissues before. Inoculation. — Microscopical 

 examination [vide p. 20 (d)] shows that the sarcoma cells can no longer 

 be found after five or six days in the immune rat. If, however, the graft 

 be removed at shorter intervals and re-inoculated into normal rats, the 

 sarcoma cells are still viable in a fair percentage of cases, after having been 

 in an immune animal for as long a period as three days (vide Table II). 



Protocol. — 0'05 c.c. of minced tumour was placed in the axillae and spleens 



Table II. 



No. of days the 

 tumour was left 

 in the normal 

 and immune 

 rats. 



The growth of 

 the tumour after 

 having been in 

 the aiillse of 

 immune rats. 



The growth of 

 the tumour after 



having been in 

 the axillsB of 

 normal rats. 



The growth of 

 the tumour after 

 having been in 

 the spleen of 

 immune rats. 



The growth of 

 the tumour after 

 having been in 

 the spleen of 

 normal rats. 



1 



8/12 



8/12 



8/12 



6/12 



2 







5/9 



8/9 



3 



6/20 



17/21 



10/18 



18/21 ■ 



6 



0/11 



90-100 per cent. 



0/11 



90-100 per cent. 



