The penetration of 50- to 60-Hz electric fields into the membrane and inter
ior of a long nerve or muscle cell is investigated analytically when the in
cident electric field is perpendicular to the length of the cell. Explicit
formulas are derived for the induced electric fields in the interior and in
the membrane. It is shown that these are comparable to those in a spherica
l cell with the same radius; that is, the induced transverse electric field
in the interior of the long cell is very small. The induced voltage across
the membrane is also determined. These results supplement earlier ones whi
ch showed that when the incident electric field is parallel to the length o
f the cell, the electric field induced in the axon and membrane is the same
as the incident field and that there is no voltage induced across the memb
rane. The combination of the induced axial and transverse electric fields p
rovides a complete picture of the induced electric field in both the membra
ne and the interior of a long cell in an arbitrarily incident electric fiel
d.