Resistance to the Growth of Cancer. 



65 



ulation of living tumor cells or of living normal cells. As Ehrlich 

 puts it, we are dealing here with a cellular immunity, which con- 

 sequently can only be caused by the live activities of the injected 

 cells. 



It has been shown by the investigations of Buchner, Sal- 

 kowsky, M. Jacoby, P. A. Levene and others, that the majority 

 of the so-called vital functions of the cell are produced by its 

 endocellular enzymes. These enzymes, while constituting an 

 integral component part of the cell, may remain under certain 

 conditions uninjured after the death of the cell. The best 

 method of liberating these endocellular enzymes consists in the 

 autolysis of tissues. 



It seemed feasible a priori that the resistance induced by nor- 

 mal mouse or rat tissue injected subcutaneously may also be due, 

 not to the function of a live cell, but to some peculiar type of an 

 endocellular ferment. With the aim in view to investigate this 

 possibility, the present research was undertaken. The work was 

 done with Ehrlich's sarcoma of a white rat, for a transplant of 

 which the author is indebted to Dr. S. Flexner. This tumor is of 

 a very malignant type and takes in from 100 per cent, to 80 per 

 cent., grows to very large size, frequently gaining the size of two 

 inches by one inch in about three weeks after inoculation. The 

 tissue used for immunization was autolyzed liver of a "Nuller" — 

 i. e., a rat naturally resistant to sarcoma. Though resistance is 

 induced by tissue of a normal animal, it was deemed advisable to 

 enhance the chances for success by taking the tissue from a resist- 

 ant animal. The liver was removed and kept under aseptic pre- 

 cautions at body temperature for two weeks ; then the autolyzed 

 liver tissue was mixed with about double the quantity of normal 

 salt solution, ground thoroughly with sand, filtered, and 1 c.c. of 

 the solution injected subcutaneously at different periods before or 

 after the inoculation of the tumor. The rats used for the experi- 

 ments were approximately of the same size and consequently of 

 about the same age. 



A diagram of the experiment follows (page 66). 



The final examination and measurement of the tumors was done 

 in about twenty-five days after inoculation, when the tumors reached 

 already the highest point of growth. These results compare quite 



