Griffith  showed that when mice were injected with a mixture of living
   avirulent bacteria are mixed with heat-killed virulent cells, the mice
   developed  pneumonia  and  died,  and  living  virulent  bacteria were
   recovered from the blood.

   The avirulent bacteria had been transformed into virulent ones.

<LI> Why  did  Griffith  not  recover  avirulent bacteria from the dead
mice?
+ The  avirulent bacteria were destroyed by phagocytic cells in
the   host's   immune   system.   However,  a  small  %  were
transformed; these multiplied and eventually killed the host.