ANIMAL EXPERIMENTATION AND PROTEAL THERAPY 277 



rats and mice, the dog that had recovered through "spontaneous" 

 regression of a tumor appeared to be immune to subsequent 

 transplantation. 



It occurred to the experimenters to test the effect of transfusing 

 the blood of such an immunized animal into the vascular system 

 of a dog in which the transplanted tumor was progressing. 

 Experiments were first made with the blood serum of the im- 

 munized dog; and the results were negative. But when, subse- 

 quently, transfusion was made of the whole blood of the dog, a 

 curative result was abserved, the tumor in the affected animal 

 regressing, and the dog going on to complete recovery. 



It seemed fairly obvious, then, that there was something in the 

 entire blood of the animal that was not conveyed with the serum 

 alone that served as an antagonist to the cancer cell. It is re- 

 called that on one occasion a not unnatural suggestion was made 

 by a visiting physician who had witnessed the results of these 

 experiments to the effect that possibly this curative principle 

 might reside in the bodies of the leucocytes. The suggestion was 

 recognized as having interest and plausibility, but the trend of 

 thought at the moment was in the direction of chemical explana- 

 tions of a less tangible kind, and no immediate attempt was made 

 to verify or refute the leucocytic hypothesis. The matter came 

 naturally to mind, however, when several years later, observation 

 was made of the modification of blood count under influence of 

 the protein treatment of human cancer subjects. 



When the series of blood counts made in my experimental 

 laboratory had reached the stage at which it became evident 

 that there were highly interesting modifications of the leucocyte 

 count (specifically characterized by an increase of mononuclear 

 leucocytes, and in particular of the large mononuclears), it 

 became a matter of interest to examine the literature of experi- 

 mentation in quest of records of analogous experiences. 



Then it became apparent that there is a peculiar paucity of 

 observations on the differential count of the white corpuscles in 

 an otherwise expansive literature ; due, no doubt, to the fact that 

 most workers have been concerned with the biochemical rather 

 than the histological aspects of the investigation. It was, I think, 

 the late Elbert Hubbard voicing a familiar conclusion who 

 made the cogent observation that, in matters of science, we 

 appear always to progress from the complex to the simple, and 

 that the obvious is the last thing to be observed. Experiments 

 in cancer inoculation with animals would seem to furnish another 

 illustration of the truth of this observation, inasmuch as very 

 tangible and obvious modifications of the blood count have for the 

 most part been overlooked by workers who were concerning 

 themselves with intricate problems of bodily metabolism involv- 



