One side of the H-bridge is as follows:
npn collector to V+, pnp collector to 0V
npn, pnp bases joined together, driven by Q1 collector (or Q2 for the
other side of the H-bridge)
npn,pnp emitters joined together, this is the center of the half-bridge
and connects to the motor (and the diodes, as originally drawn).
-------+------- +9V
|
/ c
+--| npn
| > e
| |
| +--------- to motor/diodes
| |
| < e
from Q1 collector ---+--| pnp
\ c
|
-------+------ 0V
this is basically a complementary emitter follower - the emitter voltage
is always 1 diode drop below the base voltage, which is either 0.2V (Q1
on) or 9V (Q1 off)