Fewer manual differentials are performed today because of the superior accuracy of automated differentials and because of cost and time constraints. When indicated, however, the manual differential always should be performed in a systematic manner. When the correct area has been selected, use of a back-and-forth serpentine, or “battlement,” track pattern is preferred to minimize distribution errors and ensure that each cell is counted only once. One hundred WBCs are counted and classified through the use of pushdown button counters or newer computer interfaced keypads. WBC Differential count, Blood smear, Leukocytes, Relative count, Absolute count.