32 



Scientific Proceedings (46). 



In the case of one artery and one vein, an ordinary occluding 

 ligature was first tied about the vessel, after which a transverse 

 suture was introduced about one centimeter on each side of the 

 ligature. The results in these cases did not materially differ 

 from those observed on the non-occluded vessels. No marked 

 differences were observed with different kinds or sizes of sutures. 



Microscopical results, particularly as regards the character 

 of the deposit on the foreign surfaces and the presence or absence 

 of intimal covering, will be reported later. 



13 (632) 



On tumor-immunity in rats (with demonstrations). 



By RICHARD WEIL. 



[From the Department of Experimental Therapeutics, Cornell 

 University Medical School, New York City.] 



It is the intention of the present paper to summarize briefly 

 experiments bearing on the problem of the acquired immunity 

 of rats to the implantation of tumors. In rats, as indeed in 

 practically all the other species of animals in which similar exper- 

 iments have been practicable, it has been found that the absorp- 

 tion of an implanted tumor is succeeded by a period during which 

 the animal is refractory to further implantations. The same 

 refractory condition can be induced by the injection of tumor 

 autolysates (Levin), or by the injection of suspensions of normal 

 tissue, or even of blood. The relative specificity and effective- 

 ness of these procedures vary in their details; the underlying 

 principle has been thought to be the same throughout. 



In a series of experiments with the Flexner-Jobling rat tumor, 

 I have observed certain phenomena which seem in a measure 

 to support the belief that the mechanism of immunity to the 

 tumor is identical in its biological manifestations with that found 

 in infectious disease, and is therefore mediated by immune sub- 

 stances carried by the serum. These observations may be 

 summarized as follows: 



1. Inoculation of the Flexner-Jobling adeno-carcinoma into 

 normals rats is not followed by any macroscopic evidence of 



