Surely girls couldn't join the army in 1891?

[Enumerated]

Was looking for someone else in the 1891 census when I spotted this on familysearch :
https://www.familysearch.org/ark:/61903/1:1:7PTQ-12M
A 22 year old girl apparently in the 10th Royal Hussars at York Cavalry Barracks.
I am intrigued. Unfortunately I don't have Ancestry because I would love to know what it really says on the image. Surely not? 

[JenB]

Its Henry Northcroft 

But looking at the handwriting I can understand how its been transcribed as Mary.

[Erato]

It's not impossible.  Several, possibly even hundreds, served in the Civil War.

https://www.archives.gov/publications/prologue/1993/spring/women-in-the-civil-war-1.html

[JenB]

FS have him down as female even though on the original he's a male.

[Enumerated]

Thank you for posting the original image JenB. I am surprised that the transcriber actually changed the gender to fit their misreading of the name.

[Chris Doran]

ISTR an historical programme on TV which included a girl serving as a powder monkey on a man o' war.

[Gan Yam]

There was James M S Barry, army surgeon, serving from about 1815 until 1859.  Of course nobody knew until her death that she was  Margaret Ann Bulkley, born in Ireland about 1789.