Which half? One day when I was a junior medical student, a very important Boston surgeon visited the school and delivered a great treatise on a large number of patients who had undergone successful operations for vascular reconstruction. At the end of the lecture, a young student at the back of the room timidly asked, "Do you have any controls?" Well the great surgeon drew himself up to his full height, hit the desk, and said, "Do you mean did I not operate on half of the patients?" The hall grew very quiet then. The voice at the back of the room hesitantly replied, "Yes, that's what I had in mind." Then the visitor's fist really came down as he thundered, "Of course not. That would have doomed half of them to their death!" God, it was quiet then, and one could scarcely hear the small voice ask, "Which half?" E.E. Peacock Jr., Seeing With Fresh Eyes science
The axis of movement Moving in the city means constantly changing the axis of movement. In general, lateral movement is confined to a single plane, what’s called grade, the ground level. Because circulation in multistory buildings is fundamentally one way—which is to say from the bottom up—the condition at the top is invariably different from that at the bottom. Rooftop circulation is the domain of Fantômas, of cat burglars and fleeing criminals, of lovers, and of those acrobatic enough to negotiate the gaps between buildings. Michael Sorkin, 20 Minutes in Manhattan A Burglar's Guide to the City movement