I just got back from a visit to my mom and stepdad in Maine. They’re antique dealers, and they recently scored a box full of Harper’s Weeklies from the 1860s and Woman’s Home Companions from the early 20th century. I found this ad, buried in a page full of tiny mail-order advertisements for scrofula and drunkenness cures, in a copy of Harper’s Weekly from July 25, 1868.
You might already know that embalming really took off in America around the time of the Civil War. From Wikipedia’s history of embalming:
Contemporary embalming methods advanced markedly during the American Civil War, which once again involved many servicemen dying far from home, and their family wishing them returned for local burial. Dr. Thomas Holmes received a commission from the Army Medical Corps to embalm the corpses of dead Union officers to return to their families. Military authorities also permitted private embalmers to work in military-controlled areas. The passage of Abraham Lincoln’s body home for burial was made possible by embalming and it brought the possibilities and potential of embalming to a wider public notice.
In 1867, the German chemist August Wilhelm von Hofmann discovered formaldehyde, whose preservative properties were soon discovered and which became the foundation for modern methods of embalming, replacing previous methods based on alcohol and the use of arsenical salts.
I’m not sure where “Nekrosozoic” fits in to all this, whether it was related to the discovery of formaldehyde in 1867, or if it ever really took off. It seems that its defining characteristic was that it involved applying liquid with a paint brush to the outside of the body, as opposed to injecting chemicals into the corpse via an artery.
A quick search turned up this article from the New York Times from around the same time as this ad (May 31, 1868), which describes a demonstration of the Nekrosozoic process before “a large number of medical gentlemen” at Bellevue Hospital in New York City. Some highlights:
The subject before the audience had been dead 107 days. On being cut open by Dr Janeway, the liver, lungs, heart, viscera, and fluids were found as fresh as immediately after death, and but slightly unpleasant in odor. Pieces of the liver and kidneys were handed round on plates for the inspection of those present, who applied their noses with great apparent satisfaction.
[…] A great advantage of this embalming process is, that it can be applied by any one, and is exceedinly useful in keeping bodies that have journeys to perform before burial. […]
The audience, after examining, in turn, sundry tissues of the body, through microscopes, retired much gratified.