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



of normal and immune rats. After varying lengths of time this was 

 removed ; small pieces were then taken from the margin (avoiding as 

 far as possible the necrotic centre), and placed in the axillae of normal rats. 

 The denominators of the fractions give the number of rats inoculated, the 

 numerators the number of rats in which the inoculation resulted in 

 measurable tumours. 



Besidt. — The tumour was not killed nor its subsequent growth affected by 

 exposure for three days to the living subcutaneous or splenic tissues of 

 immune rats. Exposure for six days to the tissues of immune rats prevented 

 the tumour subsequently growing. 



.3. The Effect of Experimental Alteration of Susceptible and Iiiimune 

 Animals vpon Suhsequent Inoculation. 



(a) The Injiuence of Splenectomy upon Tumour Growths. — The study of 

 the modes of growth of the sarcoma, and the observance of the immunity 

 thereto, led to a search being made for the factors which control this latter 

 condition. 



Attention was directed to the spleen, and a preliminary investigation was 

 made by extirpating this organ in normal and immune rats and seeing 

 whether any change was induced to the subsequent fate of sarcoma when 

 inoculated into such animals. 



Normal and immune rats were splenectomised and then inoculated with 

 0-05 c.c. of sarcoma at periods ranging from to 28 days after the operation. 

 The data in Table III show .that the splenectomy of normal rats does not 

 affect the subsequent growth of the tumour in them ; it shows also that in 

 immune rats the act of splenectomy does not abolish the immunity to a 

 subsequent graft. Brancati (3) and Apolant (4) have shown that with rat 

 and mouse carcinoma, splenectomy favours growth in normal animals. 



(b) The Efect of a Large Inoculation. — Whatever view may be held as to 



Table III. 



1 



j No. of rats. 



Eesult of inoculation. 





26 



17 gaye progressive tumours. 





4 gave disappearing tumours. 







5 gave oscillatory tumours. 





24 



All negative. 





35 



22 gave progressive tumours. 





10 gave disappearing tumours. 







3 gave oscillatory tumours. 



