Since about the beginning of the present century there has been much written and printed in advocacy of what the writers term ‘bacon’ hogs, and the importance if not necessity of giving more attention to their production and less to what are disparagingly designated a ‘lard’ hogs; extolling the higher prices and the virtues of lean pork and the superiority of the lean or non-fattening breeds and types, including Razor-Backs, all claimed as yielding the much-coveted streak of lean and streak of fat.
I suspect he got that material from Google Books. Google Books is useful to people who raise lard-type breeds or who want to produce pork ideally suited for cured products, because it has complete books from the 1800s and early 1900s, when lard-type hogs and fat quality were important topics.
If you just use Google Books to search for "quality of bacon", you can find all sorts of useful information, which is consistent with our modern understanding of fat quality. To demonstrate this, here are some excerpts from various books available via Google Books. Some are from the 1800s and some from the 1900s:
Experiment Station Record By U.S. Office of Experiment Stations
The Irish Industrial Exhibition of 1853 A Detailed Catalogue of Its Contents ... By Dublin. Great Industrial Exhibition (1853), John Sproule
Swine husbandry in Canada By F. C. Elford, James Burns Spencer
Treatise on the Breeding and Managemnt of Live Stock In which the Principals and Proceedings of the New School of Breeders are Fully and Experimently Discussed By Richard Parkinson
First principles of feeding farm animals a practical treatise on the feeding of farm animals: discussiing the fundamental principles and reviewing the best practices of feeding for largest returns By Charles William Burkett
Bulletin By Iowa Agriculture and Home Economics Experiment Station
Google Books is one of my favorite Google services. I appreciate it more than my local public library. It took minutes for me to round up that information. It didn't cost me anything. If one didn't have Google Books, you'd have to pay researchers to visit libraries and find the information manually, which would be completely impractical.