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these phenomena by a deficient activity of the bone-marrow, which found expression in the insufficient formation of red and white blood corpuscles. As the anatomical basis of this deficient activity, he conjectured that in this case the fatty marrow of the big long bones could not have been changed to blood forming red marrow, as is the rule in severe anaemias. In two cases the autopsy fully confirmed this diagnosis made during life. The blood platelets.--The haemoconiae. The ~blood-platelets~ were first described by Hayem, later by Bizzozero, as a third formed element of normal blood. They are roundish or oval discs free from haemoglobin. They are extremely unstable under mechanical, thermal, and chemical influences. Their size amounts to some 3 mu. Specially characteristic is their tendency, the result of their extraordinary stickiness, to run together into largish clumps, "grape clusters." This circumstance greatly facilitates the distinction of the blood platelets from the other formed elements, but renders their enumeration most difficult. The apparatus usually used for counting the blood corpuscles is, for this reason, deceptive; for the platelets rapidly cling to its walls and remain there. All early authors (_e.g._ Bizzozero) endeavoured to obviate this error by some particular diluting fluid; but a number of these elements still remained fastened to the walls of the capillary tube of the mixing apparatus. Recently Brodie and Russell have recommended a new mixture in which the platelets remain quite isolated, and are stained at the same time. They allow the drop of blood as it comes from the puncture to enter a drop of the fluid, and then estimate the relative proportion of red blood corpuscles to platelets[36]. The prescription for their solution is as follows: Dahlia-glycerin, 2% solution of common salt ... equal parts. Another method, used by the majority of more recent authors, is the relative enumeration of blood platelets in the stain dry specimen. Ehrlich found that the blood platelets were picked out by their deep red colour, corresponding to the amount of alkali they contain, in preparations treated by the iodine eosine method (see p. 46). Rabl's new method is much more complicated and in no way more serviceable, depending on a stain with iron haematoxylin recommended by E. Haidenhain for demonstration of the centrosomes. A process of Rosin's, not yet published, is more convenie
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