“…Experiments with washed platelets might be useful to clarify this point, but the rather small quantity of blood which can be collected from a shunted rat creates technical difficulties. At the present, the only sure datum is that the platelet population is lowered (13), probably owing to the deranged activity of the bone marrow (8), indicating a general depression of haemopoiesis. The implication is that, as the platelet production is reduced, there is a large population of old platelets in circulation which are known to have a decreased reactivity to aggregating agents (15,16,20) and clot retraction ability (7).…”