  Magnetization data of single crystalline La4Sr10Cu24O41 are presented. In
this compound, doped spin chains and undoped spin ladders are realized. The
magnetization, at low temperatures, is governed by the chain subsystem with a
finite interchain coupling which leads to short range antiferromagnetic spin
correlations. At higher temperatures, the response of the chains can be
estimated in terms of a Curie-Weiss law. For the ladders, we apply the
low-temperature approximation for a S=1/2 2-leg spin ladder by Troyer et al.
