by John Marshall Harlan, Chicago Railway Equipment Company v…
“ The transaction is, in legal effect, what it would have been if the maker, who purchased the cars, had given a mortgage back to the payee, securing the notes on the property until they were all fully paid. The agreement, by which the vendor retains the title, and by which the notes are secured on the cars, is collateral to the notes, and does not affect their negotiability. It does not qualify the promise to pay at the time fixed, any more than would be done by an agreement of the same kind embodied in a separate instrument in the form of a mortgage. ”
