No sign of Michael in my 1911 Motherwell Directory, which seems to be a list of householders and adult men living at the same address who were eligible to vote.
In my 1925 Motherwell & Wishaw Directory, which is split into a Householders list and in another part, there is a list of those eligible to vote, there is, at 19a Scott Street,
CURRAN Michael, steelworker. (who must be the householder).
In the 2nd section, for 19a Scott Street, there are the following adults eligible to vote.
CURRAN, MICHAEL.
CURRAN, JOHN.
CURRAN, JOSEPH.
I'm presuming the above three will be the father and 2 adult sons?
19 Scott Street was a tenement building consisting of six houses (apartments or flats, depending on where in the world you are!). 19a would have been on the ground floor.
I wouldn't have thought the street numbers went as high as 81? Could be worth checking. In this very small world, I went to school in Scott Street and now, many decades later, I do voluntary work from an office in the same street, so I know it well and can't imagine where number 81 would have been, it's a fairly short street.