302 GUY A. VOISIN AND RADSLAV KINSKY 



number of litters and have been compared: AN-BI, AN-BII, 

 AN-BIII and AN-B +T. Lyophilized tissues of newborn A mice 

 were used for immunizing injections in adult CBA mice; the 

 individual doses of each immunizing injection were: 0-25 ml. 

 in animals furnishing serum AN-BI; 0-30 ml. for AN-BII; o- 50 

 ml. for AN-BIII and AN-B + T. The animals furnishing this last 

 serum received a further graft of tumour A. 



The protective activity of these four sera was as follows: 

 AN-BI was the least powerful, by far. As can be seen in Fig. 3, its 

 action was only to delay the appearance of runting, because the 

 number of animals fmally dying in series one (facilitating serum) 

 and series two (normal serum) was almost the same, as judged on 

 day 35. Serum AN-BII gave intermediate results which were 

 very much like the overall figures presented above (Fig. i). As for 

 sera AN-BIII and AN-B +T, they were the most powerful; they 

 are considered together (Fig. 4) in order to have a number of 

 animals similar to that for serum AN-BI. The protection afforded 

 by sera AN-BIII and AN-B + T is impressive and seems to begin 

 very early. Nevertheless, even in this case, there is some remaining 

 degree of runting which leads to the death of several animals 

 between day 21 and day 28. 



It should be noted that sera withdrawn from the same mice at 

 different periods of immunization or even at intervals of a few 

 days do not always seem to have the same degree of activity. 



Another important fact concerning the quality of the sera is 

 that several freezings and thawings of the sera result in a decrease 

 of their protective power and require an increase in the doses used. 



(b) Dose of serum. The influence of the dose of serum on the 

 degree of protection against runting has not been systematically 

 studied. Nevertheless, we have relevant data concerning serum 

 AN-BI, which was used at four doses : o- 20; o- 25 ; o- 50 and i • 00 

 mm.^ While doses of o- 20 and o- 25 had no protective effect, but 

 only caused a slight retardation in the occurrence of runting, doses 

 of o- 50 and i-oq had both a retarding effect and defmite pro- 



