These results were first published in 1924 and then revised and republished in 1931 in the work cited above. Many old pictures and sculptures show a horse tossing back his head in an effort to get air. In it the harness strap passes around the base of the horse's neck. Though this horse is drawing a light chariot, it was assumed that its gaping mouth and bulging eyes were typical of the reactions of horses who had to pull heavier loads. Spruytte argued that the Romans used two harnesses, one a neck collar and the other a dorsal yoke that used a breast strap.
Some background is needed here.
For some time there had been disputes between medieval historians and archaeologists and those studying ancient Rome. The horse-collar was often cited as a major example of a problem that the Romans were unable to solve. Now armed with Spruytte's work, classical archaeologists began to rework a good bit of the older material in addition to producing new studies. The classical archaeologists now produced evidence that the Romans had indeed developed a variety of carts and did harness horses in tandem. They have little doubt that the Romans had invented these things, but medievalists still argue that their use was not common.