Final answer:
The x-axis of a Coulter counter histogram shows side scatter related to cellular fluorescence intensity (logarithmic scale), while the y-axis represents the number of cells, depicted as forward scatter.
Step-by-step explanation:
On a Coulter counter histogram, the x-axis represents the side scatter which corresponds to the cellular fluorescence intensity of each cell. The fluorescence intensity is on a logarithmic scale, indicating that with each unit increase along the axis, the fluorescence intensity increases by a factor of 10. On the y-axis, the forward scatter is plotted, which represents the number of cells in a sample at a particular level of fluorescence. Such histograms are typically used in flow cytometry to analyze populations of cells tagged with fluorescent markers. In the provided example, two peaks are observed; the left peak with lower fluorescence represents cells without CD8 expression, while the right peak with higher fluorescence indicates cells with CD8 expression due to antibody binding.