What is The Train to the North from Torreon?

Thousands of people from all over the Republic of Mexico are boarding the long line of cars at the same time. The train has brought cattle south for the war effort, and the poor people are allowed to go back toward the United States in the tall, empty cattle cars. However, the cars have just been emptied, and there is still manure thick on the floors, and the people have to shovel it out with their bare hands before they can enter. There is no water to wash the cars, so the people remain in the slick mess left behind by the frightened cattle.