Contents

11 January 1985
Vol 227, Issue 4683

About The Cover

Computer-enhanced, light micrograph of a spleen tissue section containing microspheres (blue) consisting of albumin, magnetite, and an entrapped peptide messenger. The microspheres were injected intravenously and became localized in the spleen. Here, the release of the messenger results in attraction of blood neutrophils (red), which accumulate around the spheres and become activated to enhance the local resistance to infection. See page 182. [D. F. Ranney, University of Texas Health Science Center, Dallas, Texas 75235]