336 



B. NAKIC, A. KASTELAN AND N. AVDALOVIC 



* Day of complete rejection of cross-graft(s). 



t Test-grafted 3-4 weeks following breakdown of tolerance. 



% Placed two weeks after rejection of first test-graft. 



§ As judged by colour, adherence to graft bed and survival time. 



II Torn off by host on 4th postoperative day. 



Attempts to increase the incidence of tolerance in Y59 

 parabionts by preimmunization of Wistar rats 



Wistar rats were preimmunized with spleen cell suspension 

 from Y59 donors. Five days later donors were joined in para- 

 biotic union with the immunized recipients and cross-grafts 

 exchanged. The parabionts were separated after six days. 



The purpose of the experiment was to give Wistar parabiotic 

 partners an artificial advantage whereby an increase in the inci- 

 dence of tolerance would be gained. As can be seen from Table 

 IV, no such increase has been obtained but four animals developed 

 symptoms of "parabiotic disease" and died with well preserved 

 grafts. Anaemia was absent in these cases and the sick animals 

 appeared red because of the general capillary dilatation; the cross- 

 graft although normally coloured looked pale by comparison. 

 This "red form" of the disease ran a less acute course than the 



