Fractional probability distribution functions of the size of the major axis (left) and aspect ratio of clouds (middle) found in the 250 μm maps of the Hi-GAL survey (Molinari et al. 2016; Elia et al. 2017; full line) and in the ¹²CO FCRAO HCS survey (Heyer et al. 2001; Dib et al. 2009; dashed line). The distribution of column density contrast is assumed to be a power law. The distributions of L₁ and f are fitted with parameterized functions. The values of the parameters of the fit are reported in the main text.