Haemoglobin is the part of the blood that carries oxygen to the tissues.
Haemoglobin was first described in 1825 but its ability to carry oxygen was found in 1840 by Huenefeld. Too little haemoglobin (Hb) leads to anaemia – a shortage of blood cells or Hb.
The first form of assessing anaemia was by simply looking at the person and the colour of their lips, tongue and fingernails. This physical assessment was refined by examining a smear of blood under the microscope.
There are several methods to estimate haemoglobin.
The Sahli method uses diluted hydrochloric acid to create the brownish coloured acid haematin which is then diluted to match a colour scale. This is the method used in the Hellige haemoglobinometer.
Another method used solutions of copper sulphate of different strengths. A drop of blood was put into the solution and the strength of the solution in which it just floated was the amount of haemoglobin. This method, using one standard strength, was used for many years at the blood bank to screen donors.
The Talquist scale was another quick – but very inaccurate – method that used blotting paper soaked in blood and compared with a standard colour chart.
Modern methods and the easy availability of pathology tests have rendered these methods obsolete but most older GPs will have used one or another in their practice.