In the end, there was nothing to be done. It turned out that little Christmas Eve had a large, cancerous, inoperable tumor in her abdomen that had already spread to her lymph nodes. On Friday, Susie and I spent some time with her, stroking her and talking to her, and then we took her to the vet, where very quickly and painlessly, as we stood there, she was put to sleep.
These past two days, when we return to our apartment, it seems barren and lonely. It is not a large apartment -- 1500 square feet, more or less -- but she was, at her best, only ten pounds, and she took up very little space. Indeed, truth to tell, we sometimes had to go searching for her to find where she had settled down -- under the bed, under a chest, in a closet, on a chair.
It is much too soon to think about getting another cat. She was found up a tree in Amherst, Massachusetts, on Christmas Eve, seventeen years ago [hence the name]. We offered to look after her for the weekend, and she never left.
I understand that it is odd for two mature, sophisticated adults to lavish so much emotion on a little black and brown long-haired cat, but there it is. We shall miss her greatly.