74 



Scientific Proceedings (32). 



of the horse, rabbit, guinea-pig, calf, and sheep are equally affected. 

 The differences become well marked after a few minutes' exposure 

 to the different temperatures, and thereafter bringing them to one 

 temperature fails to equalize the hemolysis even after many hours. 

 The effect, then, is on the corpuscle rather than on the surround- 

 ing fluid and is exerted chiefly in the first moments of exposure. 



Temperatures above 37° C. act variously according to the 

 particular species whose blood is used. Horse corpuscles give 

 distinctly more hemolysis at 42° C. than at 37° C. The cor- 

 puscles of the guinea-pig and the calf give still less hemolysis at 

 43° C. than at 37° C. 



33 (371) 



A carcinoma of the rat (Flexner-Jobling) considered from 

 the standpoint of immunity. 



By F. P. GAY. 



^From the Laboratory of the Cancer Commission of Harvard 

 University.'] 



Experiments have been in progress for the last year and a half 

 with the Flexner-Jobling rat tumor for the purpose of gaining some 

 insight as to the normal and artifically produced conditions of 

 resistance to this tumor. 



The tumor as originally described by Flexner and Jobling was 

 a sarcoma and later became carcinomatous in structure. It has 

 shown no marked variations in histological structure during the 

 eight generations which we have cultivated it. White rats from 

 different dealers varied considerably in their susceptibility to in- 

 oculation with this tumor. Animals from the most susceptible 

 source gave 100 per cent, of "takes" whereas the next most sus- 

 ceptible strain gave only 50 per cent. Following inoculation into 

 the region of the axilla metastases occur regularly in the lungs 

 but rarely in the adjacent lymph-nodes. The time of occurrence 

 of metastases would seem to be relatively constant in the most 

 susceptible rats. Metastases occur later and at more irregular 

 intervals in less susceptible animals. 



The tumor may be transplanted from the metastases and such 

 "metastatic" tumors would seem after several generations to have 



