Using a new and unique multiparticle detection device, we have measured the average final state multiplicity for a sample of 1,500 events from the reaction pp → pp (nw<super>±</super>) at 28.5 GeV/c where both protons were constrained to limited regions of phase space. We find that the resulting average charge multiplicity depends linearly on the recoil mass from both protons, and on the inelasticity. A rapidity analysis indicates that low multiplicity final states are produced by one fragmenting proton, while as the multiplicity increases, so does the probability of the other proton also fragmenting. No evidence was found for multiperipheral production. We compare our data with events in which only one proton is constrained and find that the multiplicity varies with the behavior of both final state protons, the higher multiplicities occurring for more central collisions. / Ph. D.