32 Susceptibility of Hats towards Jensen's Rat Sarcoma. 



resistance to the growth of the tumour is in some cases set up in the 

 human suhject. 



The bearing of our observations upon malignant disease in the human 

 subject is of a dual nature. If the role which the lymphocyte plays in 

 immunity towards Jensen's rat sarcoma proves to apply also to the human 

 malignant growths, then the lines along which successful treatment may 

 possibly be attained are to some extent indicated. In the first place, it may 

 be possible by stimulating the growth of lymphoid tissues to produce a 

 concentration of these cells at the locality of the growth. This might be 

 accomplished by the inoculation of malignant cells rendered harmless by 

 irradiation or of some other material. 



In the second place, reference may be made to the treatment of 

 malignant disease by means of X-rays or the rays from radium (/3- and 

 7-rays). The aim of radiotherapy in malignant disease is to cause the 

 destruction of the maliguant cells with a minimum amount of damage to the 

 adjacent normal tissues. Under many conditions of irradiation of the human 

 subject, and especially in the treatment of deep-seated malignant growths, it 

 happens that the normal tissues are subject to a very considerable degree of 

 irradiation. 



In view of the fact that the lymphocytes play an important part in the 

 healing of growths of Jensen's rat sarcoma, and because these cells have 

 been shown to be especially vulnerable to these radiations, it follows that 

 particular care should be taken in this treatment of cancer in the human 

 subject to protect the rest of the body from radiation, more especially those 

 parts where lymphocytes occur, namely, the blood, lymph, bone marrow, 

 lymphatic glands, and spleen. 



It is known (8) tha.t a small dose of rays may stimulate the production of 

 some of the cellular constituents of the blood. With prolonged irradiation, 

 however, the probability of destroying cells which are capable of resisting 

 the growth of the invading cancer cells suggests the advisability of taking 

 steps to avoid the irradiation of any but the malignant tissues, and, if possible, 

 to restrict the blood supply of all these tissues, malignant or otherwise, 

 through which the radiation penetrates. 



The expenses of this research were partly defrayed by a grant to one of 

 us (S. E.) from the Eoyal Society. 



