l checked his venous pressure and shock level.

As he finished, Dal felt the Black Doctor's eyes on him. "It's going to
be all right," he said. "There'll be time for help to come."

Feebly the Black Doctor shook his head. "No time," he said. "Can't wait
that long." Dal could see the fear in the old man's eyes. His lips began
to move again as though there were something more he wanted to say; but
then his face hardened, and he turned his head away helplessly.

Dal walked around the bed and looked down at the tracing, comparing it
with the first one that was taken. "What do you think, Tiger?"

"It's no good. He'll never make it for five more hours."

"What about right now?"

Tiger shook his head. "It's a terrible surgical risk."

"But every minute of waiting makes it worse, right?"

"That's right."

"Then I think we'll stop waiting," Dal said. "We have a prosthetic heart
in condition for use, don't we?"

"Of course."

"Good. Get it ready now." It seemed as though someone else were
talking. "You'll have to be first assistant, Tiger. We'll get him onto
the heart-lung machine, and if we don't have help available by then,
we'll have to try to complete the transplant. Jack, you'll give
anaesthesia, and it will be a tricky job. Try to use local blocks as
much as you can, and have the heart-lung machine ready well in advance.
We'll only have a few seconds to make the shift. Now let's get moving."

Tiger stared at him. "Are you sure that you want to do this?"

"I never wanted anything less in my life," Dal said fervently. "But do
you think he can survive until a Hospital Ship arrives?"

"No."

"Then it seems to me that I don't have any choice. You two don't need to
worry. This is a surgical problem now, and I'll take full
responsibility."

The Black Doctor was watching him, and Dal knew he had heard the
conversation. Now the old man lay helplessly as they moved about getting
the surgical room into preparation. Jack prepared the anaesthetics,
checked and rechecked the complex heart-lung machine which could
artificially support circulation and respiration at the time that the
damaged heart was separated from its great vessels. The transplant
prosthetic heart had been grown in the laboratories on Hospital Earth
from embryonic tissue; Tiger removed it from the frozen specimen locker
and brought it to normal body temperature in the special warm saline
bath designed for the purpose.

Throughout the preparations the