DEPARTMENT OF GENETICS. 



125 



experiments by Dr. Strong have shown that this tumor grows in a very- 

 high percentage of mice inoculated. A few wild mice which are non- 

 susceptible have been obtained and experiments will at once be started 

 to determine the genetics of susceptibility and non-susceptibility of 

 this tumor. 



Inoculation of mice of the genera Peromyscus and Microtus. — Miss 

 Pearl Anderson and Miss B. W. Johnson have, under Dr. Little's 

 direction, trapped and inoculated with tumors a number of mice, both 

 Peromyscus novenihoracensis and Microtus pennsylvanicus. The tumors 

 used have been adenocarcinoma dbrA, dbrB, and sarcoma 180. None 

 of the mice grew any of the tumors progressively, but certain of them 

 showed indications of a mass at the site of inoculation. Table 6 

 shows the percentage of indications ( + ) for the two genera and the 

 three tumors. There was no evidence of stimulation of the host tis- 

 sue to neoplastic growth. 



Table 6. — The absolute number of field mice of each of two genera in which an indication of 

 the inoculated tumor remained (-(-) and in which no indication remained ( — ); also the 

 percentage of persisting indications. 



Preliminary work on the isolation of single tumor cells and on the 

 mechanics of metastasis. — During the summer, Mr. George 0. Gey, of 

 the University of Pittsburgh, has worked in Dr. Little's laboratory 

 on the isolation and implantation of minute particles of tumor tissue, 

 with a view to isolating single tumor-cells if possible. The prehminary 

 phases of the technique have been thoroughly gone into and the work 

 will be continued throughout the year at Pittsburgh by Mr. Gey. 

 Miss Margaret Schneider has also assisted in this work. 



An interesting piece of evidence as to the mechanics of metastases 

 was obtained by Mr. Gey in the course of his w^ork. He reports 

 somewhat as follows : 



"Tumor emulsion filtered through fine gauze was inoculated through an 

 hypodermic syringe into the liver of 5 mice. The dosage ranged from 0.2 c.c. 

 to 0.3 c.c. of filtered emulsion. Great care was taken throughout the opera- 

 tion to maintain as aseptic conditions as possible. In every case the mice 

 were killed 14 days after inoculation. All showed abnormal appearances of 

 liver, kidneys, and spleen. The two controls which remained available for 

 observation had been inoculated subcutaneously and both showed tumors. 



"In the experimental animals histological examination showed that the 

 sarcoma has definitely invaded, through the medium of the blood, the liver, kid- 



