Continuity mistake: During McCoy's struggle with the orderly, only half of the plastic colored bottles strewn on the table are knocked off onto the floor. But when Nurse Chapel hurries over to tranquilize the orderly, the rest of the bottles vanish, leaving the table completely clear. (00:19:10)
Continuity mistake: Sulu's hooded viewer is up as he reports that the Defiant is starting to drift. In the next shot, a reverse angle showing the screen, the viewer disappears. This recurs throughout the episode. (00:06:10)
Continuity mistake: When Kirk is being beamed aboard near the end, the crewman operating the transporter has a single lieutenant's stripe. But in the close-up of his hands on the controls, the stripe changes into the braid of a lieutenant commander. (00:46:40)
Continuity mistake: After Spock nerve pinches Chekov when he goes mad and he is taken to Sickbay, the Tholian ship appears and hails the Enterprise. When Spock says "on main viewer," the shot of Loskene is on the screen, but the back of Chekov's head can be seen when it should be in Sickbay.
Continuity mistake: When Checkov turns on the viewer in the transporter room, the Defiant is seen directly from the starboard side, when it should have been seen from the quarter profile port side, as it was drifting to the Enterprise's port side.
Continuity mistake: When Kirk, Bones, Chekov, and Spock go over to the Defiant, the suits they have on have a black support bar in the left side of the headpiece. When the camera looks down at the dead men and back to Kirk, you see the bar is on the right, and his hair is parted on the right. The very next look at Kirk, the bar and the part of his hair is back on the left.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.