It's not a whole heck of a lot different from 1935 until now.
From (2008) NEC 240.21(B)
(2) Taps Not over 7.5 m (25 ft) Long. Where the length of
the tap conductors does not exceed 7.5 m (25 ft) and the tap
conductors comply with all the following:
(1) The ampacity of the tap conductors is not less than
one-third of the rating of the overcurrent device protecting
the feeder conductors.
(2) The tap conductors terminate in a single circuit breaker
or a single set of fuses that limit the load to the ampacity
of the tap conductors. This device shall be permitted
to supply any number of additional overcurrent devices
on its load side.
(3) The tap conductors are protected from physical damage
by being enclosed in an approved raceway or by other
approved means.
