The low standard of medical education in the South makes this theory quite plausible.
We now formed the acquaintance of a species of human vermin that united with the Rebels, cold, hunger, lice and the oppression of distraint, to leave nothing undone that could add to the miseries of our prison life.
These were the fledglings of the slums and dives of New York--graduates of that metropolitan sink of iniquity where the rogues and criminals of the whole world meet for mutual instruction in vice.
They were men who, as a rule, had never known, a day of honesty and cleanliness in their misspent lives; whose fathers, brothers and constant companions were roughs, malefactors and, felons; whose mothers, wives and sisters were prostitutes, procuresses and thieves; men who had from infancy lived in an atmosphere of sin, until it saturated every fiber of their being as a dweller in a jungle imbibes malaria by every one of his, millions of pores, until his very marrow is surcharged with it.
They included representatives from all nationalities, and their descendants, but the English and Irish elements predominated.

They had an argot peculiar to themselves.

It was partly made up of the "flash" language of the London thieves, amplified and enriched by the cant vocabulary and the jargon of crime of every European tongue.

They spoke it with a peculiar accent and intonation that made them instantly recognizable from the roughs of all other Cities.

They called themselves "N'Yaarkers;" we came to know them as "Raiders." If everything in the animal world has its counterpart among men, then these were the wolves, jackals and hyenas of the race at once cowardly and fierce--audaciously bold when the power of numbers was on their side, and cowardly when confronted with resolution by anything like an equality of strength.
Like all other roughs and rascals of whatever degree, they were utterly worthless as soldiers.