Reactive Power of the White Rat. 



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The reactive power of the white rat to tissue implantation. 

 Second communication. 



By ISAAC LEVIN. 



[From the Department of Pathology of Columbia University, at the 

 College of Physicians and Surgeons.] 



At the November meeting of the New York Pathological 

 Society, 1 I reported briefly on a series of experiments I have un- 

 dertaken on white rats, with the aim to investigate whether the 

 great success attained lately in the transplantation of malignant 

 growths from one rat into another is not due, in part at least, to 

 the different behavior of the organism of the white rat to tissue 

 implantation, as compared with other laboratory animals. 



The majority of the workers who have experimented with the 

 tumors of the white mouse or rat seem to be of the opinion that 

 the success in the transplantations of these tumors is due to the 

 great intrinsic power of limitless proliferation of the cells of these 

 tumors, and they ignore the possible cellular reaction of the organ- 

 ism of the host to the implanted tissue. But the fact that pieces of 

 the same tumor from the same rat or mouse grow readily on white 

 mice of one race, and not at all on the white mice of another race ; 

 the fact, further, that while the original tumor, when implanted, 

 grows in only about 10 per cent, of animals used, and, when 

 re-implanted, it grows in 90 per cent., and some other similar in- 

 stances, seem to indicate, a priori, that the white mouse or rat 

 reacts differently to implantation of tumor, as well as of normal 

 tissue, than the other laboratory animals. 



My first set of experiments consisted in the implantation of nor- 

 mal tissue from one animal into another. Pieces of skin, liver, 

 spleen, testicle, or mammary gland are implanted under the skin 

 or in the peritoneal cavity of another animal. In the great ma- 

 jority of the experiments (about 60 to 75 per cent.) the pieces 

 remained unabsorbed for as long as three weeks, even when, as in 

 the peritoneum, they do not become attached anywhere, but float 

 like a foreign body. Usually, the pieces are either surrounded by 



'Levin : Medical Record, December 14, 1907. 



