356 PAUL S. RUSSELL 



significant alteration in reactivity from the normal to tissues of the 

 donor strain. 



Since most of the animals die promptly and without reaching a 

 body weight of more than about 3 or 4 g. the gross appearance of 

 the animals is not as strikingly abnormal with this combination of 



14 RUNTS 

 5-10 million DBA/I spleen l/V 



14 16 18 20 22 24 26 28 2 4 6 8 10 12 14 16 18 20 22 

 (^) DAYS OF AGE (5) 



Fig. I. Left: The course of weight gain of 12 normal newborn C57BL/6 



mice. The curve is roughly linear. 



Right: The weight-gain curve of 14 newborn C57BL/6 mice given 5 to 10 



million DBA/i spleen cells intravenously within 12 hours of birth. The 



"plateau period", after which there is Uttle further gain in weight, begins at 



the sixth or seventh day. 



Strains as with some others (Billingham, 1958). Acutely ill animals 

 show some loss of hair and a slight scaling of the skin, a change 

 which becomes more obvious in those which live a little longer 

 (Fig. 3). The abdomen is somewhat protuberant and a few mice 

 suffer from diarrhoea. Examination of the abdominal contents of 

 animals killed when moribund often reveals small collections of 



