Histogram reflecting the distribution of spheres observed by microscopy in normal liver parenchyma of Pt 2. Six biopsies from Pt 2, with a total volume of 36 mm3, divided into 60 slices were investigated. Bars show the number of clusters found with each size, i.e. spheres per cluster. Fifty-three percent of all 793 spheres found were located within any of the larger clusters (8 to 59 spheres/cluster).