  We use the combination of photometric and spectroscopic data of 47 Tuc stars
to reconstruct the possible formation of a second generation of stars in the
central regions of the cluster, from matter ejected from massive Asymptotic
Giant Branch stars, diluted with pristine gas. The yields from massive AGB
stars with the appropriate metallicity (Z=0.004, i.e. [Fe/H]=-0.75) are
compatible with the observations, in terms of extension and slope of the
patterns observed, involving oxygen, nitrogen, sodium and aluminium. Based on
the constraints on the maximum helium of 47 Tuc stars provided by photometric
investigations, and on the helium content of the ejecta, we estimate that the
gas out of which second generation stars formed was composed of about one-third
of gas from intermediate mass stars, with M>= 5Mo and about two-thirds of
pristine gas. We tentatively identify the few stars whose Na, Al and O
abundances resemble the undiluted AGB yields with the small fraction of 47 Tuc
stars populating the faint subgiant branch. From the relative fraction of first
and second generation stars currently observed, we estimate that the initial FG
population in 47 Tuc was about 7.5 times more massive than the cluster current
total mass.
