They run over and under one another and sleep in heaps, and sniff one another with their quivering noses. The mouse feeder tells us that if you put a strange mouse into one of their cages, one with the wrong, alien scent, they will bite it to death. The cellar smells strongly of mouse droppings, a smell which wafts upward through the whole building, getting fainter as you go up, mingling with the smell of the green Dustbane used to clean the floors, and with the other smells, the floor polish and furniture wax and formaldehyde and snakes. We don’t find any of the things in the building repulsive. The general arrangements, though not the details, are familiar to us, though we’ve never seen so many mice in one place before and are awed by their numbers and stench. We would like to get the turtles out of their pool and play with them, but since they’re snapping turtles and bad-tempered and can take your fingers off, we know enough not to. My brother wants an ox eyeball out of one of the jars: it’s the sort of thing other boys find impressive. Some of the upstairs rooms are labs. The labs have vast ceilings and blackboards across the front. They contain rows and rows of large dark desks, more like tables than desks, with high stools to sit on. Each desk has two lamps with green glass shades, and two microscopes, old microscopes, with heavy thin tubing and brass fittings.

We’ve seen microscopes before, but not at such length; we can spend a lot of time with them before getting tired of them. Sometimes we’re given slides to look at: butterfly wings, cross-sections of worms, planaria stained with pink and purple dyes so you can see the different parts. At other times we put our fingers under the lenses and examine our fingernails, the pale parts curved like hills against their dark pink sky, the skin around them grainy and creased like the edge of a desert. Or we pull hairs out of our heads to look at them, hard and shiny like the bristles that grow out of the chitonous skins of insects, with the hair roots at the end like tiny onion bulbs.