I found this interesting instruction in a Caledonian Rule book from 1863. If you would like to know a bit more about the transportation of dogs by rail in the Victorian era, I wrote a whole post on the topic last year. However, there seems to have been very little written on the topic, so I am open to expanding my knowledge on it.
When greyhound or other large dogs are booked by a train, and they can neither be placed in the carriage boots, nor chained in the van, they must be locked in the compartment of a second or third class Caledonian local carriage, with their attendants and not where there are other passengers. If "booked through," they can be changed at the terminal station.