IMMUNOLOGY 



859 



antibody or acquire a resistance to it. So far, the reproduction-inhibiting 

 properties of ablastin have not been demonstrated in vitro, but suitable 

 amounts of serum, containing ablastin together with adult trypanosomes, 

 when tested in vivo in a rat allow the trypanosomes to live, but prevent 

 them from reproducing. (Adult trypanosomes have to be used for this 



5eedRal 97 z 



EiperirnQnldl Rar 977 





Conirol Ra; 9 80 



, -^- ^r-* 



2 4 6 8 

 Daijs after Inieclioa 



10 U 14 



Figure 190. The demonstration of ablastin against Trypanosoma lewisi by passive 

 transfer. The rate of reproduction of the trypanosomes, as shown by the constant coeffi- 

 cient of variation, is completely inhibited in experimental rat 977, which received 2 cc. 

 of serum and a large number of adult trypanosomes from seed rat 972 ; whereas the rate 

 of reproduction goes through the normal cycle in control rat 977, which received a 

 similar number of adult trypanosomes, but no serum, from seed rat 972. (From W. H. 

 Taliaferro, 1924.) 



test since a curtailment of the reproductive activity of dividing trypano- 

 somes, which is all that could be expected, is difficult to demonstrate with 

 certainty. ) Thus the difference between the coefficient of variation curve 

 in experimental rat 977, which was given ablastic serum plus adult 

 trypanosomes, and in control rat 980, which was given normal serum 

 plus adult trypanosomes, is seen in Figure 190. The number curve re- 



