What Is a Hemocytometer?

What Is a Hemocytometer?

A hemocytometer is a glass or plastic slide with a chamber of known volume, and often gridlines of known spacings, generally used for counting several types of cells. Concentration of the cells can also be determined in the source they were sampled from, using a hemocytometer.

The word “hemocytometer”–also spelled “hema-”, “haemo-”, or “haema-”–comes from the Greek root words ha?ma (“blood”), kytos (“container” or “body”, generally used for cells), and métro (“measure”) from which we also get words like “meter”. So, it should come as no surprise that this tool was originally developed for the purpose of counting blood cells. Indeed, the development of the hemocytometer was closely tied to that of the medical field of hematology–the study of blood and related diseases.

Most of the early work in hematology was done in France in the late 18th and early 19th centuries because many investigators there had an interest in blood-associated diseases. Since contemporary French physicians were generally not trained scientists, they saw the use of microscopes for clinical medicine as impractical. The rise of hemocytometry happened in mid-19th-century Germany, where clinicians had already made the transition from feeling patients’ issues, to laboratory medicine.

The first published method of counting blood cells was accomplished by Karl Vierdordt in 1852, and involved drawing blood into a tube of known internal diameter. The length of the blood-filled portion of the tube was then measured, allowing calculation of the volume. Next, the blood was expelled from a tube to let it dry on a glass plate. Finally, the cells were counted on the plate, using a microscope featuring a square micrometer, so the viewer could see the square in the microscope view. Vierdordt was able to use this method to calculate that his own blood had about 5.17×109 cells/mL, which we now know to be in the normal range for an adult male!

Improvements and add-ons to this method were later adopted, which eventually resulted in the modern hemocytometer. One of the first modifications was replacing the tube and glass plate with a counting chamber of known volume–the first true hemocytometer. A counting chamber in lieu of the tube and plate, allowed cells to fill the chamber by capillary action, making their distribution more uniform and the counts more reliable as a result. Rulings were incorporated directly onto the glass slide, eliminating the need for microscopes with finely calibrated ocular rulings; including gridlines of known width on a square of known size, to make the counting process more convenient. In order to count the cells as they all appeared at the same moment in time, a microphotograph was taken, as a means of getting the most accurate representation. Further modifications included connecting a secondary mixing chamber with a pipette and suction mechanism to make an early “lab-on-a-chip.” Splitting the chamber into two parts made counts easier to replicate. A more recent innovation replaces the glass slides with disposable plastic slides <link to product category page for “Counting Slides”> that don’t run the risk of contamination, which could skew the results, among other benefits <link to “5 Advantages of Disposable Over Reusable Hemocytometers” article> and using machines to count the cells so researchers don’t have to waste time manually counting. With significantly larger white blood cells, more gridlines  spaced further apart enabled researchers to use hemocytometers for them.

Today, hemocytometers are also used for other types of cells. They can be used when culturing mammalian, plant, or bacterial cells; preparing the yeast for beer fermentation; or obtaining sperm counts. Whatever the use for a hemocytometer, you can have confidence in the technology that has been through nearly 170 years of improvement. In fact, the automated counters have gotten good enough that they don’t need gridlines at