Continuity mistake: When McCoy places the old tricycle down on the ground, the handlebars are facing the right with its wheels facing the left. When McCoy is attacked by the diseased Only, Kirk and Spock subdue him, and as he lies on the ground the tricycle flips over between shots, so the handlebars suddenly end up facing the left. (00:04:30)
Continuity mistake: After the wild man is down on the mound, his right hand is under his body. In the close up, it's on the frame of the trike. (00:05:05)
Continuity mistake: As Kirk and Spock head towards the Only, they first approach him from the same side. When the camera cuts to a different angle, they are approaching from different sides. (00:05:09)
Continuity mistake: The ropes tying Yeoman Rand to the chair keep changing positions (above her elbows or below her elbows) between shots. (00:39:40)
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.