Irish Blood Transfusion Service Service. The frequency of blood groups in Ireland is as follows: It is important that the IBTS collects enough O Rh D positive blood as almost half the population are that blood type. Donors with O Rh D negative are known as universal donors. Their blood can be transfused to patients of any other blood group in an emergency or if the patient's own blood group is unavailable. Because any patient can receive O Rh D negative blood, the IBTS need to have extra O Rh D negative blood available at all times. The service depends entirely on voluntary donations
Blood blood clotting in a transparent container. When blood is drawn in a glass container and left undisturbed for about an hour, four different layers can be seen. A dark clot forms at the bottom (the "black bile"). Above the clot is a layer of red blood cells (the "blood"). Above this is a whitish layer of white blood cells (the "phlegm"). The top layer is clear yellow serum (the "yellow bile"). The ABO blood group system was discovered in the year 1900 by Karl Landsteiner. Jan Janský is credited with the first classification of blood into the four types (A,