Iefluence of Digitonin upon Growth of Carcinoma. 145 



water, collecting the precipitate, washing it in water and drying 

 over H2SO4 at 36 0 C. The substance which was thus obtained 

 was pure white. It is soluble in alcohol and forms unstable sus- 

 pensions in water. One c.c. of a I per cent, suspension injected 

 subcutaneously in rats produced no symptoms whatever, either 

 local or general. A solution in alcohol precipitated cholesterol 

 from alcoholic solution, and a suspension in water coagulated a 

 suspension of cholesterol in N/100 sodium oleate. 



Fourteen rats with carcinoma, which had been inoculated 20 

 days previously, were divided without selection into two lots, 

 the one lot of 5 served as controls, the other of 9 received 1 c.c. 

 of a 1 per cent, suspension of the above preparation of digitonin 

 in m/6 NaCl, injected directly into the tumors on the 20th, 21st, 

 22d, 23d, 25th and 26th days after inoculation. As in the previous 

 experiment, the earlier injections caused softening and discolora- 

 tion of the tumors. The tumors soon hardened, however, and 

 thereafter grew much more rapidly than the tumors in the controls, 

 as the following figures reveal : 



20 days after 25 days after 29 days after 



inoculation inoculation. inoculation. 



Controls 100 no 126 



Digitonin 100 147 168 



We interpret these results in the following way : When digitonin 

 is injected into the tumor it first of all renders inactive the cho- 

 lesterol then within the tumor and this results in softening and 

 incipient degeneration of the tumor. The precipitated cholesterol 

 is, however, replaced by cholesterol from the surrounding tissues 

 and body-fluids, and the cholesterol bound by the digitonin is 

 retained within the tumor and gradually liberated from its com- 

 bination with the digitonin, with the result that cholesterol is 

 concentrated within the tumor, and the growth of the tumor is 

 thereby accelerated. The fact that lecithin prevents the accelera- 

 tion of the growth of the tumor by digitonin is in harmony with 

 the above interpretation and with our previous results showing 

 that lecithin and cholesterol have opposite actions upon the 

 growth of carcinoma. 1 



1 T. Brailsford Robertson and Theodore C. Burnett, Proc. Soc. Exper. Biol, 

 and Med., 10 (1912), p. 59; Journal of Exper. Med., 17 (1913), p. 344. 



