I've just discovered that Susan Hill's lovely book The Magic Apple Tree - from which comes this passage - has recently been re-issued as an ebook for Kindle (and it's a bargain, too). Mine was a library copy, so I'm glad to know it's more widely available again.
Nothing to do with that, but Abebooks have a nice article here, The Dog and the Novel: Loyal Companions, to which I've linked before but which you may not have come across. Interesting to note the contemporary novels which feature dogs, including The Story of Edgar Sawtelle which Pam Ayres chose when she appeared on My Life in Books.
And speaking of dogs, has anyone read Elizabeth von Arnim's memoir All The Dogs Of My Life? It opens thus: "I would like, to begin with, to say that though parents, husbands, children, lovers and friends are all very well, they are not dogs ...Once [dogs] love, they love steadily, unchangingly, till their last breath. That is how I like to be loved. Therefore I will write of dogs."