Received: 12 August 2021
Revised: 15 September 2021
Accepted: 24 September 2021
DOI: 10.1002/cyto.a.24505
COMMUNICATION TO THE EDITOR
The Coulter Principle: A history
Marshall Don. Graham
Nicholasville, Kentucky, USA
Abstract
Correspondence
Marshall Don. Graham, 115 Patton Court,
Nicholasville, Kentucky 40356, USA.
Email: don.graham@twc.com
A historical description of Wallace H. Coulter's invention and development of his
companies' instrumentation for analysis of blood cells or particles has never been
available, and too often, this void has been addressed by conjectural or promotional
publications. A history thesis, based on the author's access to Coulter's personal
papers and to files kept by his father, Joseph R. Coulter, Sr., has recently become
available; for the first time Coulter's developmental process is factually detailed
against the historical context in which it occurred. This paper is an introductory overview of that developmental process as discussed therein. It should be of interest to
not only the ISAC membership, but to Cytometry's broader readership as well.
KEYWORDS
blood-cell counting, Coulter Counter©, Coulter Principle, hematology analyzers, Wallace
Coulter
In October 1948, Wallace H. Coulter demonstrated that individual
hematology analyzer (Table 1), the Coulter Counter® Model S, succes-
blood cells, when appropriately suspended in saline solution and flowed
sors to which now daily analyze millions of patients' blood samples. In
through a small aperture through which an electrical current was also
1978, he became a charter member of the International Society for
flowing, could be sensed via the transient changes their throughflow
Analytical Cytology (ISAC), and in addition to his other recognitions
produced in the current [1, p. 1058]. These cellular signals could be
[3, pp. 189–190], in 1993, he received one of the Society's first two
processed electronically to provide count and volumetric data for the
Distinguished Service Awards for his significant contributions [4].
cells while a specific volume of the suspension flowed through the
Although Coulter only published the one paper publicizing his
aperture (Figure 1). Over the next several years, he implemented this
efforts [2], to protect improvements made during the developmental
Coulter Principle in the first commercially-available automated blood-
process he contributed as an inventor to 85 U.S. patents. These and
®
cell counter, the Coulter Counter Model A, which he introduced in his
details in his personal papers are the only record of this developmen-
presentation at the 1956 National Electronics Conference in Chicago.
tal work he himself left. Regrettably, many of his papers were appar-
Acceptably limiting coincidental passage of multiple cells through the
ently discarded or lost during Coulter Corporation's move from
aperture required sample dilutions yielding maximum counts of some
Hialeah, FL, to Kendall, FL, in 1992–1994. Consequently, attempts to
50,000 cells, or a cellular throughflow of about 3,300 cells per second,
document the history of those early phases of the Coulter story have
whereas a conventional manual count of 500 cells required perhaps
been persistently conjectural or promotional rather than factual [1].
20 min. The automated count repeatably reduced count errors to one-
However, included among those personal papers were ones that sup-
tenth of those for manual counts done by expert technologists, this by
port Coulter's motivation being accurate and rapid blood-cell counts,
a method that not only required less-skilled technologists, but needed
a motivation inspired by the need to effectively monitor bone-marrow
only 1.25% of the count time [2].
recovery from radiation exposure such as endured by survivors of the
Coulter then guided the ground-breaking Model A counter
through
incremental
development
into
the
first
automated
Hiroshima and Nagasaki atomic bombings of August 1945.
During my service as Coulter's technical advisor from mid-1978
until Beckman Instruments bought and merged with Coulter Corpora-
Based on research as a Donovan Fellow for the MA degree in history at the University of
tion in late 1997, he provided access to personal papers he kept in his
Kentucky, Lexington. The Donovan Program provided all required tuition.
Hialeah office. My collection of those papers began in 1982 when he
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© 2021 International Society for Advancement of Cytometry
Cytometry. 2022;101:8–11.
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GRAHAM
F I G U R E 1 Simplified overview of sample processing in the Coulter Counter® Model A. Current to the sensing electrodes was provided from
the main amplifier via a resistance. The threshold circuit allowed counting and display of all amplified signal pulses above a desired value;
incrementing it enabled cumulative volume distributions. When the stopcock of the liquid-handling portion was manually opened, a vacuum
source caused the sample to begin flowing from the beaker through a small aperture into the sample tube and the level of the mercury in the left
tube of the manometer to be lowered beneath the lower control electrode through the manometer wall. When the stopcock was manually closed,
the sample continued flowing as the mercury contacted first the lower, then the upper, control electrode to start and stop the pulse counting
circuitry while returning to its equilibrium position above the upper electrode
TABLE 1
process
Instruments in Coulter's incremental development
constitutes a major part of the thesis discussion and will be summarized in the following text. As of this writing, there have been 469 the-
Coulter
Counter®
Thesis [5]
figure
User reports
countries; as a charter member of ISAC, I believe that it will also be of
Model A
Figure 5.2
Mattern et al. [6]; Brecher et al. [7]
interest to many readers of Cytometry.
Model B
Figure 8.1
Brecher et al. [8]; Sipe and Cronkite [9]
sis downloads in the United States and a further 244 among 61 other
Model A signal processing produced a series of signal pulses
Model C
Figure 8.4
Lines and Wood [10]; Princen [11]
from a controlled sample volume flowing through the aperture
Model D
Figure 8.5
Blades and Flavell [12]; Belsky et al. [13]
simultaneously with quasi-constant current from the main ampli-
Model F
Figure 8.6
Valeriote et al. [14]; Rice et al. [15]
fier's constant-voltage power source (Figure 1). Signal pulses were
Model S
Figure 8.7
Barnard et al. [16]; de Lange et al. [17]
thus sensitive not only to nonliquid components of the sample, but
Note: In the Models A, B, C, D, and F, the liquid-handling portion of
Figure 1 was also provided a second manually-operated stopcock through
which clean electrolyte solution could flush the sample tube free of
sample that had flowed through the aperture as a result of the first
stopcock's function. In the Models A, B, and C, the liquid-handling portion
was implemented in a separate sample stand; in the Models D, F, and S it
was internal to the electronics cabinet. To keep the sample suspension
from settling, in industrial versions of the Models A, B, and C the liquidhandling portion was often provided with a propeller-shaped stirrer blade
in the beaker that was driven by a variable-speed electric motor [5, p. 81].
also to variations in aperture geometry, temperature of the aperture's environment, the temperature-dependent resistivity of the
suspending diluent, and with some diluents frequently required by
industrial suspensions, polarity-dependent polarizations of the
sensing electrodes. To eliminate pulses from small contaminating
particles in the diluent and thermal noise from the instrument electronics, the pulses were amplified by a circuit that eliminated pulses
below an adjustable amplitude threshold before passing them to
the counting and display circuitry. By incrementally increasing the
threshold setting and recording the count for sequential sample
runs, an operator could manually generate a cumulative volume dis-
either gave me or permitted my photocopying items from his personal
tribution for the nonliquid sample constituents of interest. How-
files while I drafted his nomination as a Fellow of the Institute of Elec-
ever, the sequential sample runs required considerable amounts of
trical and Electronics Engineers (IEEE). This information, plus that
both sample and operator time, and the cumulative distributions
gleaned from his father's files, enabled not only [1], but also summa-
were less desirable than differential distributions. While the latter
ries of both Coulter's family background and the aforesaid develop-
could be derived from the former, arithmetical calculations often
mental process [3] and my history MA thesis detailing the latter
tainted the result with significant errors.
through his introduction of the Model S [5]. The liquid-handling por-
To minimize pulse sensitivity to the aforesaid factors, the Model
tion of the evolving Coulter instrumentation is summarized in the
B counter was provided with a truly constant aperture current and a
Note for Table 1; evolution of the signal-processing portion
current-sensitive main amplifier. It was also provided with a second
10
GRAHAM
threshold circuit, whereby the operator could increment a differential
excellent statistical repeatability. However, if the cellular signal stream
distribution bin over sequential sample runs; while this did not greatly
from one aperture differed significantly from those from the other
reduce either required sample volumes or operator time, it minimized
two like apertures, for example, due to a partial aperture blockage,
calculation errors. And when the movable bin was controlled by a
that aperture's results were voted out of the data to be averaged, and
sequencing 4-s timer, an accessory Model H plotter could automati-
the technologist was warned of the discordant signal stream.
cally accumulate 25-bin differential volume distributions from
Although the reported counts then depended on only two cellular sig-
constant-flow sample runs lasting some 100 s, with the pulses and
nal streams, their accuracy was still significantly better than provided
counts within individual bins being displayed. While these circuitry
by earlier methods. The cellular counts provided the sample's white-
improvements in the Model B counter and the innovative capability of
cell count (WBC) and red-cell count (RBC). The latter was used to cal-
the Model H distribution plotter offered improved analytic efficiency,
culate the average volume of the red cells (MCV) and combined with a
the lengthy sample runs and time required to sequentially acquire the
hemoglobin measurement (Hb) from the white-cell bath to yield the
bins of differential distributions prompted the next step in Coulter's
volume percentage of red cells (hematocrit, Hct, or packed cell vol-
developmental process.
ume, PCV), the average mass of hemoglobin per red cell (MCH), and
The Model C counters included multiple pulse-height analyzer cir-
the ratio of Hb to Hct (MCHC). For the first time it was possible to
cuits that simultaneously collected data for up to 12 differential vol-
efficiently assess a patient blood sample via rapid, accurate, and
ume bins from a single sample run; only a few of these large and
repeatable automated determinations of these seven blood parame-
expensive instruments were ever sold. However, they demonstrated
ters, which were printed within less than a minute of the technologist
the feasibility of this approach, and experience gained in developing
presenting the blood sample.
them facilitated design of the transistorized replacement for the
Here I have only outlined Coulter's journey from his comprehen-
Model A, the Model F counter discussed below, and the smaller and
sion of the critical need for accurate, repeatable, and rapid blood-cell
more versatile Model T counter once integrated circuits replaced dis-
counts through his invention, implementation, and commercialization
crete transistors.
of the groundbreaking Model A counter and its incremental elabora-
Market competition prompted design of the Model D counter as
tion into the revolutionary Model S hematology analyzer. The thesis
a simplified, low-cost alternative for the Model A in smaller hematol-
[5] provides much greater detail regarding that journey and the
ogy laboratories. This dual-function counter provided switch-
shifting historical context in which it occurred.
selectable modes, one optimized for red-cell counts and the other for
white-cell counts, and was the first Coulter Counter® to integrate the
CONFLIC T OF INT ER E ST
sample stand into the electronics cabinet. Subsequent versions incor-
The author has no conflict of interest to declare regarding this
porated transistors and then integrated circuits; some of these later
Communication.
instruments permitted broader application than the original Model D
counter.
The transistorized Model F counter then replaced the aging
OR CID
Marshall Don. Graham
https://orcid.org/0000-0002-5236-8064
Model A counter in many hematology laboratories. Accessory modules enabled rapid computation of the mean cell volume (MCV) and
hematocrit (Hct) of a blood sample; the Model M volume converter
calculated the total nonliquid volume above threshold in the sample
being counted. To allow checking the aperture for clogs, an internal
optical system projected an image of the aperture onto a screen in the
operator's view, so eliminating the microscope similarly used in the
four earlier counter models.
To use the Model S hematology analyzer, the technologist had
only to present a blood sample to a sample probe and initiate the
automated process. Venous blood samples were diluted appropriately
for a white-cell count, then split, the red cells in one part being lysed
before it was sent to one bath while the other part was diluted appropriately a second time for a red-cell count and sent to a second bath.
The two dilutions were each drawn through three Coulter apertures,
of 100-μm diameter for white-cell analysis and of 70-μm diameter for
red-cell analysis. The signal streams from the six apertures were analyzed and corrected for coincidence; if there were no inconsistencies
in any aperture signal stream, those from the three like apertures were
forwarded to independent counting circuits, the results from which
were then averaged to provide rapid and accurate counts with
RE FE RE NCE S
1. Graham MD. The Coulter Principle: imaginary origins. Cytometry A.
2013;83A:1057–61.
2. Coulter WH. High speed automatic blood cell counter and cell size
analyzer. In: Proceedings of the National Electronics Conference, Vol.
12. Chicago: National Electronics Conference, Inc.; 1957, p. 1034–40.
Reprinted in: Lichtman MA, editor. Hematology landmark papers of
the twentieth century. San Diego: Academic Press; 2000, p. 913–21.
3. Graham MD. The Coulter Principle: the Arkansas background. Arkansas Hist Quart. 2014;73:164–91.
4. The International Society for Analytical Cytology later became the
International Society for Advancement of Cytometry (also ISAC).
Dean PN. SAC charter members. List dated July 28, 1978. Dean
PN. A history of the International Society for Analytical Cytology.
Cytometry A. 1996;24:301, 306 and Cytometry A. 2004;58A:4,
5, and 8.
5. Graham M. The Coulter Principle: for the good of humankind 2020.
Theses and dissertations—history. 62. https://uknowledge.uky.edu/
history_etds/62. Brewer NW of the IEEE History Center has now
edited this and archived it on the ETHW. https://ethw.org/
Archives:The_Coulter_Principle:_For_the_Good_of_Humankind.
6. Mattern CFT, Brackett FS, Olson BJ. The determination of number
and size of particles by electronic gating: blood cells. J Appl Physiol.
1957;10:56–70.
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GRAHAM
7. Brecher G, Schneiderman M, Williams GZ. Evaluation of an electronic
blood cell counter. Am J Clin Pathol. 1956;26:1439–49.
8. Brecher G, Jakobek EF, Schneiderman MA, Williams GZ. Size distribution of erythrocytes. Ann N Y Acad Sci. 1962;99:242–61.
9. Sipe CR, Cronkite EP. Studies on the application of the Coulter electronic counter in enumeration of platelets. ibid. 1962;99:262–70.
10. Lines RW, Wood WM. Automatic counting and sizing of fine particles. Ceramics. 1965;16:17–30.
11. Princen LH. Improved determination of calibration and coincidence
correction constants for Coulter counters. Rev Sci Instrum. 1966;37:
1416–8.
12. Blades AN, Flavell HCG. Observations on the use of the Coulter
model D electronic cell counter in clinical haematology. J Clin Pathol.
1963;16:158–63, 292.
13. Belsky JL, Ishimaru T, Ohashi T, Robertson TL, Taniguchi B. Leukocyte
response to exercise in atomic bomb survivors. Radiat Res. 1972;50:
699–707.
14. Valeriote FA, Collins DC, Bruce WR. Hematological recovery in the
mouse following single doses of gamma radiation and cyclophosphamide. Radiat Res. 1968;33:501–11.
15. Rice FAH, Lepick J, Darden JH. Studies of the action of leucogenenol
on the myeloid and lymphoid tissues of the sublethally irradiated
mouse. Radiat Res. 1968;36:144–57.
16. Barnard DF, Carter AB, Crosland-Taylor PJ, Stewart JW. An evaluation of the Coulter model S. J Clin Path. 1969;22(suppl 3):26–33.
17. de Lange JA, Rutten EPF, Schmidt NA, Eernise JG, Veltkamp JJ. Automation in the hematology laboratory. J Clin Chem Clin Biochem.
1976;14:485–97.
AUTHOR BIOGRAPHY
Marshall Don. Graham served as technical advisor to Wallace
H. Coulter from June 1978 to November 1997, then served as
principal staff development scientist with Beckman Coulter, Inc.,
Miami, until his retirement in December 2011.
How to cite this article: Graham MD. The Coulter Principle: A
history. Cytometry. 2022;101:8–11. https://doi.org/10.1002/
cyto.a.24505