Railway spine was a nineteenth-century diagnosis for the post-traumatic symptoms of passengers involved in railroad accidents. The first full length medical study of the condition was John Eric Erichsen's classic book, On Railway and Other Injuries of the Nervous System. For this reason, railway spine is often known as "Erichsen's disease". Railway collisions were a frequent occurrence in the early 19th century. Exacerbating the problem was the fact that railway cars were flimsy, wooden structures with no protection for the occupants.