These brushes have been scanned at 300dpi from the Pictorial Archive of Printer's Ornaments: from the Renaissance to the 20th Century (Dover Pictorial Archive Series) by Carol Belanger Grafton. The images are, to the best of my knowledge, free for artists and designers to use royalty free. The brushes in this set are just a small sample from the wonderful collection of Renaissance, Baroque, Victorian, and Art Nouveau designs in this archive.
To read the first few pages of this lovely resource, visit Amazon
For a tutorial on how you can create, save and load your own brushes in Adobe Photoshop, please visit this Tucows article