368 PAUL S. RUSSELL 



chosen. This is a large dose, the daily subcutaneous administration 

 of which from birth was alone observed to cause the death of 4 of 

 10 newborn C57BL/6 mice within the first two weeks. The deve- 

 lopment of those animals which survived cortisone treatment was 

 only slightly delayed, however. In Fig. 14 the weight gain of 16 

 runts treated daily with tliis dose of cortisone is compared with 



S 2 



o 



RECEIVING II- 16 MILLION CELLS 

 and 0.025 mg/gm CORTISONE/DAY 

 (16 animals) 



RECEIVING 11-16 MILLION 

 CELLS l/V ONLY 



(15 animals) 



2 4 6 8 10 12 14 16 18 20 22 



DAYS OF AGE 



Fig. 14. Weight-gain curves of two groups of C57BL/6 mice both receiving 11 

 to 16 million DBA/i spleen cells intravenously at birth. Each curve expresses 

 the mean w^eight of the survivors present at each stage and the bars show a single 

 standard deviation of the mean. The numbers in parentheses are the survivors 

 present. The group represented by open circles received 0-025 mg./g. of corti- 

 sone acetate subcutaneously each day. A t test of the two groups on the twelfth 

 day indicates a statistical difference between them (P< 0-005) 



that of 15 animals wliich had also received 11 to 16 million 

 homologous spleen cells on the first day of life but had not been 

 treated with cortisone. As time goes on a difference between these 

 groups appears which increases until both treated and untreated 

 animals are overcome by the advancing disease. The greatest 

 difference in the mean weights of the two groups was at 16 days 

 but even at 12 days, when a larger number of animals was 

 surviving, a simple t test revealed that the two groups differed 



