Which preposition to use with vertebras

of Occurrences 2%

It is difficult to write stylistically a per-annum report of 1,327 curvatures of the spine, whereas the poor specific little vertebra of Mamie O'Grady, daughter to Lou, your laundress, whose alcoholic husband once invaded your very own basement and attempted to strangle her in the coal-bin, can instantly create an apron bazaar in the church vestry-rooms.

at Occurrences 1%

He had caused the driver of each of them to be provided with a sharp iron spike and a mallet, and had given orders that every beast that became unmanageable, and ran back upon his own ranks, should be instantly killed by driving the spike into the vertebra at the junction of the head and the spine.

for Occurrences 1%

When we went the other Sunday evening, we could see no one in it; but after a hymn had been sung, a spring seemed to be touched, and up jumped the parson, who had been reclining on his dorsal vertebra for eight minutes at the rear.

Which preposition to use with  vertebras