The polytropic index &ggr; is a key parameter in the modeling of interplanetary magnetic clouds. In contrast to other models, the self-similar model of Osherovich et al. [1993a> suggested &ggr;<1 in clouds. The first measurements [Osherovich et al. 1993b> showed that &ggr;≈&ggr;e=0.4--0.5 in magnetic clouds demonstrating the dominant role of electrons over protons (Te/Tp≈6-7 at 1 AU). For the January 10--11, 1997 cloud observed by WIND, we found that the polytropic relation Te=FNe&ggr;e-1 is valid with &ggr;e=0.52¿0.04 and F=1.97 105¿0.12 105 (cgs units) over the number density range 1<Ne<10 cm-3. The constant F is half the value found for other clouds studied at 1 AU, while &ggr;e is essentially the same. We believe that the small value of F should be attributed to a later stage of the self-similar evolution of this cloud as compared to other clouds studied previously at 1 AU.