Here's why the saying became common:
* Glue was a significant product: In those days, horsehide glue was a valuable commodity used in various industries like furniture making, bookbinding, and construction.
* Horses were valuable assets: People invested a lot in horses, and losing one could be financially and emotionally difficult.
* Euphemism for difficult truth: Saying a horse was "sent to the glue factory" was a way to soften the blow of its death. It was less harsh than saying "the horse was slaughtered" or "the horse died".
However, the practice of using horse hides for glue has significantly decreased:
* Synthetic glues: Modern glue production relies heavily on synthetic materials, making horsehide glue less essential.
* Animal welfare concerns: The practice of using animal hides for glue has also come under scrutiny due to ethical concerns about animal welfare.
Today, the phrase "sent to the glue factory" is mostly used humorously or ironically, as it is rarely the actual fate of old or injured horses. Many organizations and individuals provide rescue and sanctuary for horses that are no longer able to work.