He's showing minimal side effects. Tests on his bone marrow indicate that the chemotherapy is working.

What is in the marrow is hard to take out of the bone

HONEY: (Apologetically, holding up her brandy bottle) I peel labels.
GEORGE: We all peel labels, sweetie; and when you get through the skin, all three layers, through the muscle, slosh aside the organs (An aside to NICK) them which is still sloshable--(Back to HONEY) and get down to bone...you know what you do then?
HONEY: (Terribly interested) No!
GEORGE: When you get down to bone, you haven't got all the way, yet. There's something inside the bone...the marrow...and that's what you gotta get at. (A strange smile at MARTHA)

Bone marrow transplant is moving forward slowly,

The subordinate is likely to feel that the examiner has taken a sample of his bone marrow.

Laughter is a tranquilizer with no side effects.