I am ninety. Or ninety-three. One or the other. When you're five, you know your age down to the month. Even in your twenties you know how old you are. I'm twenty three, you say, or maybe twenty-seven. But then in your thirties something strange starts to happen. It's a mere hiccup at first, an instant of hesitation. How old are you? Oh, I'm-you start confidently, but then you stop. You were going to say thirty-three, but you're not. You're thirty-five. And then you're bothered, because you wonder if this is the beginning of the end. It is, of course, but it's decades before you admit it.
You start to forget words: they're on the tip of your tongue, but instead of eventually dislodging, they stay there. You go upstairs to fetch something, and by the time you get there you can't remember what it was you were after. You call your child by the names of all your other children and finally the dog before you get to his. Sometimes you forget what day it is. And finally you forget the year. (Sara Gruen, Water for Elephants)
What is ‘his’?: your child’s dog? And what does the whole clause mean?