For fiction no subject-card is necessary.

On the other hand, many books have to do with more than one subject; a volume of essays, for example, or a group of biographical sketches.

For such it is desirable to add to the subject-list by writing as many cards for each book as the importance of the several subjects therein and the space the author gives to them seem to demand.

Each card will have for the first word of its entry the subject to which it refers, followed by the author and title of the book.
Arrange these cards also alphabetically with all the others.

Put on every card in the catalog the call-number of the book to which it refers.