Isthmus.........................................
Nursing and sales are professions associated with the lower middle class.
Answer:
The camel, possibly
Explanation:
No animal is known as "the sheep of the desert" as far as I can tell, but the camel is sometimes called "the ship of the desert".
Communications in the late 1800s were restricted. The earliest postal systems were often run by a local citizen out of his house. Postal carriers traveled by horse and only carried documents.