512 MARY B. STARK 



It is possible that the death of all the larvae into which the sus- 

 pension was injected may be partly due to the toxic effects of 

 the tumor cells injected and partly due to the effects of tumors 

 developed from the suspension. The larvae did not hve suffi- 

 ciently long to allow the growth of tumors large enough to be 

 seen with the naked eye, but some development must have taken 

 place. The adult tissues of the fly are more resistant than those 

 of the larvae and are not so much affected by the toxic products 

 of the tumor-cell suspension. The flies continue to five suffi- 

 ciently long to allow the development of a tumor from the in- 

 jected tumor cells. Death occurred sooner or later, however, 

 and it is evidently due to the development of a tumor from the 

 injected cell suspension. 



MEAL-WORM INOCULATION 



Hoping to increase the percentage of tumors developed from 

 tumor-cell suspension, it occurred to me to inject the suspension 

 into larger insects. The meal worm was tried, since it is easily 

 obtained and lives as a larva two years, a period more than 

 long enough for the development of a tumor. 



The tumor-cell suspension was prepared as before. The meal 

 worms were washed in alcohol and kept in sterile Petri dishes 

 until the wounds healed. The inoculation was normally made 

 between the seventh and eighth pleurites. Two sets of controls 

 were used: one Locke's solution and the other normal-cell sus- 

 pension in Locke's solution. Two weeks after the inoculation, I 

 noticed in many of the worms that had received the tumor-cell 

 suspension the appearance of small black spots. These spots 

 were often near the place of inoculation, but were also found in 

 other regions of the body. Some of these worms were killed and 

 the regions with spots were fixed, sectioned, and stained. Mi- 

 croscopic examination revealed the fact that they were abnormal 

 growths. A section through the growth, as in figure 2, shows the 

 center to be made up of a necrotic area surrounded by a new 

 growth of the connective-tissue cells of the meal worm. All 

 the growths examined were similar in structure.' It looks as 



