This is a photo of the "traction engine" that frightened the veterinary community so much at the turn of the Century; much as Dr. Hines' use of the Internet frightens the Texas Board and the AVMA today. Over the years, the machine's name was shortened to the word, "tractor".

Traction engines began to replace draft horses in the 1850s, reducing veterinarian incomes. They were coal-fired steam behemoths. By the time a distinguished veterinarian of the time wrote an article you can read here , farmers were replaced them with tractors powered by internal combustion motors. By 1917, Henry Ford, having already replaced carriage horses with his Model T, offered one (the Fordson) to US farmers.  By 1925, steam-powered tractors were a thing of the past. Had veterinarians of that day and age had the option, they might well have outlawed tractors as well.