# In major squares, and each square is one millimeter

In the Clinical Lab module, a hemocytometer is used. This device was invented by Louis-Charles Malassez. The meaning of hemo is blood, cyto is cell, and meter for measuring. Therefore a hemocytometer is used for measuring blood cells. A hemocytometer is a square chamber carved onto a piece of glass. The chamber contains a grid of perpendicular lines. The hemocytometer is split up into nine major squares, and each square is one millimeter squared. The middle of the counting area contains twenty-five large squares, which each have sixteen smaller squares. The hemocytometer is placed under a microscope stage and the counting grid is brought into focus.When it comes to counting the cells, you only count those that are on the lines of two sides of a larger square to ensure that you don’t count a cell twice. The suspensions should be properly diluted so that cells don’t overlap on the grid, and to ensure that they are evenly distributed throughout. In order to tell the difference between the dead and living cells, the sample is usually diluted with a stain, for example, Trypan Blue. This process colors the dead cells blue. When viewed through the microscope, you will notice that some cells will appear as dark blue, which indicates the dead cells. When counting make sure you have a large enough magnification to recognize the cells and then begin to count them in selected squares to get a count around 100, which is the minimum amount needed for a significant count. If a cell overlaps on the top or right count it as “in”, however it overlaps on the bottom or left rule it as “out.” After gathering your cell count, you can then find the cell concentration using the formula; total cells (ml)= counted cells * (dilution factor/the number of squares) * 10,000 cells/ml. Using a hemocytometer is a long and tedious process. It has been used for over 100 years by cell biologists in order to count cells. Today the hemocytometer is made up of an improved Neubauer grid and they are a staple in cell biology labs. However, today automated cell counters are beginning to replace hemocytometer devices. These offer more reliable results and take far less time. The prices of hemocytometers vary depending on quality. Cheaper devices may seem to work fine, but eventually you will have inaccurate counts and they have a higher chance of breaking. The prices range from \$30 to \$270. There are several brands and websites that carry hemocytometers. When preparing to buy a hemocytometer you want to look for three things, durability, accuracy, and how difficult it is to use. In addition to the main purpose of a hemocytometer, which is counting cells, there are many other applications of a hemocytometer device. They can be used to perform blood counts and sperm counts. It can also be used to process cells for culture, process cells for downstream analysis, and to determine the size of a cell. Due to the variety of uses for this device, they are continued being used today.