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A continuum limit treatment of planar spin chains with arbitrary S ispresented. The difference between integer and half-integer spins is emphasised.While isotropic half-integer spin chains are gapless,and have power-law decayof correlations at T = 0 with exponent eta = 1, integer spin systems have asinglet ground state with a gap for S=1 excitations and exponential decay ofcorrelations. The easy-plane to easy-axis transition is described.  Note: this is a verbatim transcription of ILL preprint SP-81/95, which iscited in a number of places, but was rejected for publication in 1981, andremained unpublished in this original form, which gives somewhat differentarguments for the central result as compared to the later paper finallypublished in Phys. Lett. 93A, 464 (1983); many thanks to Jeno Solyom forpreserving this historical document.

Ground State Properties of Antiferromagnetic Chains with Unrestricted Spin: Integer Spin Chains as Realisations of the O(3) Non-Linear Sigma Model