Quote Originally Posted by nsdfrv View Post
In the period of serfdom the cattle owned by a landlord was numbered in heads or 'по головам', while peasants (serfs) owned by him were numbered 'по душам' for statistics. E.g. "Сколько душ имеете?" ('How many serfs/persons do you own?'). This number of persons or peasant population owned by a landlord (количество душ) was important for keeping statistics, and was also the indicator of the landlord's status or wealth. Today we still count cattle 'по головам' 'Душа (населения)' in your example means a unit for population statistics; the term itself is outdated.
Perfect historical explanation