i can't get through to the other side

If his katra had sensation and memory when trapped in the mind of Dr. McCoy, it would have experienced the same phenomenon as he is currently feeling (feeling? feeling! indeed...): that of being able to witness events occurring and process information related to his surroundings, but not being able to control or act at all in accord.

Standing opposite him, so very often, with a poorly-concealed smile on top of even more poorly concealed abject grief, was the individual most acutely poised, at all times, to bring Spock around to the truest mechanism of himself.

As if...beyond irradiated glass.