In 1971, the Mayo Clinic Routine Hematology Laboratory put into service a new instrument—the Coulter Model S—which automatically determined red and white cell counts, hemoglobin, hematocrit, mean cell volume, mean cell hemoglobin, and mean cell hemoglobin concentration.
All seven determinations were made on a single 1.3 ml. blood sample and the results were automatically imprinted on a form which was attached to the patient’s chart. A carbon copy of the report was also made which was retained in the laboratory. Samples were introduced into the instrument at the rate of two to three per minute.
Automation was not new to the Hematology Laboratory. Use of earlier model Coulter Counters for red and white blood cell count was started about ten years prior and represented a vast improvement over the procedure by which a technician literally counted the number of cells visualized through a microscope. However, to secure all of the results obtained in less than a minute with the Model S required approximately 8 minutes with the earlier automatic methods.
The new instrument incorporated the measuring devices of six Coulter Counters. The instrument aspirated 1.3 ml. of blood from the sample tube. Most of this blood was used to flush out the previous sample from the system and only a small portion of it was used for the determinations. The blood was diluted and mixed within the diluter module and was propelled through the system by a pneumatic power supply. Measuring devices responded with signals which were translated electronically into numbers which appeared on the imprinted form.