Final answer:
The 19th century was transformative for thoroughbred horsing, as horses were central to transportation and the military until technological advances, like electrified streetcars, began to supplant their roles. Eadweard Muybridge's photographic studies enhanced the understanding of equine biomechanics, while the changing nature of warfare reduced the use of cavalry.
Step-by-step explanation:
The 19th century saw significant developments in thoroughbred horsing. This era was marked by a deeper integration of horses into various aspects of daily life, even as technological advancements gradually started to replace them. Horses were essential for transportation, both in cities for commuter travel and in the military where they were part of cavalry units.
Despite the advent of public transportation systems such as commuter railways, a temporary increase in the number of horses in cities was observed as they were needed to pull streetcars from rail stations to people's final destinations within the cities. The electrification of streetcars and the building of underground railroads ultimately reduced the reliance on horses in urban centers. Notable improvements, like the introduction of electrified streetcars in New York City in 1881, marked the beginning of this transition.
Moreover, the works of Eadweard Muybridge, such as the photographic study of a thoroughbred mare "Annie G." galloping in 1887 and "Sallie Gardner" in motion in 1878, revolutionized the understanding of horse locomotion and contributed significantly to the knowledge of equine biomechanics. These accomplishments during the 19th century demonstrated the wide-spanning impact that thoroughbred horsing had on society—from transportation and the arts to advancements in military tactics and technology, which by the end of the 19th century reduced the military use of cavalry.