392 COCA AND GILMAN. 



Among the more recent investigations upon immunity to tumors, 

 those of von Dungern - are perhaps the most significant in their bearing 

 upon the problem of immunization against cancer in human beings. 



Von Dungern excised a young, rapidly growing, moderately malignant sarcoma, 

 which had been derived originally from a wild hare, and had been transplanted 

 to the laboratory rabbit, and inoculated with it two groups of rabbits. Group 

 A consisted of normal, i. e., hitherto unused animals; group B had been previously 

 inoculated with an emulsion of an identical tumor derived from another trans- 

 plant. Among the second group Avere animals in which the tumor resulting 

 from the first inoculation was still present, as well as animals in which the 

 resulting growth had been excised, or had been spontaneously absorbed, and also 

 animals in which the first inoculation had failed altogether. Although every 

 individual of group A developed large tumors, in not one animal of group B was 

 the second inoculation successful. 



Furthermore,, the tumors still present in some of the members of 

 group B, which were derived from the primary inoculation, softened 

 after the second injection of tumor material and were converted into 

 sterile abscesses. 



The predominant cell found in these softened tumors was the macrophage, 

 which was accompanied by a few lymphoid and plasma cells. 



Von Dungern believed that the immimity against the second inoculation was 

 due to the development in the previously inoculated animal of a condition of 

 hypersensitiveness, as a result of which the second introduction of tumor ma- 

 terial was met with an exaggerated local inflammatory reaction. He thought he 

 could demonstrate, at the site of the second injection, the presence of nonspecific 

 cytolytic substances which he considered to be produced locally as a part of 

 the exaggerated reaction. 



The chief object of all studies upon immunity against cancer is, 

 naturally, the finding of some means by which this fearful disease in 

 human beings may be successfully combated. 



"Wliile all these experimental results are suggestive in their bearing 

 upon the cancer problem in this restricted sense, none of them correspond 

 strictly with the conditions existing in human beings afflicted with this 

 disease. In man we are dealing with primary growths, whereas in 

 lower animals the experiments have all been made with transplanted 

 tumors. 



The all-important problem of cancer research has yet to be solved, 

 namely, is it possible to immunize human beings against their own 

 primary malignant growths? Experiments that throw light upon this 

 question have already been published. 



The earliest of these were those of Metalnikoflf, who in 1900 demonstrated 

 the production in guinea pigs that had been injected with guinea pig's testicle, 

 of specific antibodies which were capable of destroying the spermatozoa of the 

 same animal. Following these studies, von Dungern and Hirschfeld,' after having 



" Ztschr. f. Immunitatsf. Orig. (1909), 2, 391. 

 'Centralbl. f. BaJct. etc. Ref. Beilage zu AU. I. Jena (1909), 44, 57. 



