in Figure \[M55slx\]) is in good agreement with the models and our MFs. From these curves, we have that the slope of the high-mass end of the global MF of M55 is $x\simeq-1.0$, which is in quite good agreement with the global value of the MF found from the global LF of M55 ( previous section). In Figure \[profile\] we show the model which best fits the observed radial density profile for a global mass function with a slope $x=-1.0$.

The relatively flat MF of M55 could be the result of the selective loss of main sequence stars, especially from the outer envelope of the cluster, caused by the strong tidal shocks suffered by M55 during its many passages through the Galactic disk and near the Galactic bulge [@Piotto93 for a general discussion of the problem]. A flat MF for M55 agrees well with the results of [@CPS93] who have found that the clusters with a small $R_{GC}$ and/or $Z_{GC}$ show a MF significantly flatter than the cluster in the outer Galactic halo or farther from the Galactic plane. Indeed, M55 is near to the Galactic bulge, $R_{GC}=4.7$ kpc ($R_\odot=8.0$ kpc), and to the Galactic disk $Z_{GC}=-2.0$ kpc. Figure \[m55xrz\] 