372 



PAUL S. RUSSELL 



A series of 41 newborn C57BL/6 animals was then treated with 

 three injections of 0-37 mg./kg. (or a total of about 2 [jLg. per 



17,400,000 DBA CELLS 



G. 



10 



2 - 



0.37mg/kg 

 ^methotrexate s/c 

 days If3 bt 5 



Untreated Control 



}0. 75 mg/kg metho- 

 trexate s/c day I 



20 



Days of Age 



30 



Fig. 15. Individual weight-gain records of a litter of 7 

 newborn C57BL/6 niice all of which received 17 milHon 

 DBA/ 1 spleen cells on the first day of hfe. The control 

 died promptly of runt disease. Single injections of 

 amethopterin (methotrexate) (0-75 mg./kg.) were 

 ineffective in checking the onset of runt disease. Three 

 injections of amethopterin (0-37 mg./kg.) given on the 

 first, third and fifth days of Hfe allowed four animals to 

 develop at a normal rate. 



mouse) over the first five days of life following neonatal injections 

 of approximately 15 million DBA/i spleen cells. As indicated in 

 Table I, 59 per cent of these animals survived. Those wliich 

 died tended to do so later than untreated runts. Although many 



