The influence of anticoagulants on fibrin network formation.

In general the method described by Fonio and Schwenderer (1942) was used. Ten ml. of blood taken from a fasting patient with a dry syringe was divided equally and put into two paraffined test tubes which had been kept in a refrigerator. Thereafter the blood was centrifuged for 2 minutes at 3,000 revolutions per minute. The plasma thus obtained was transferred in a dry, carefully cleaned pipette to a slide which had been sprinkled lightly with particles of burned kaolin powder under observation by a dark-field microscope. The kaolin particles were added to provide crystallization centres and focusing points. The preparation was then covered with a polished coverslip and observed by means of an oil-immersion objective in which an iris diaphragm was incorporated. Two test-tubes were used because it had been found that the second sample frequently clotted spontaneously during centrifuging, a behaviour which could possibly be explained by the presence of bubbles of froth formed in expressing the blood from the syringe; this factor might well influence blood-clotting. The microscope was focused either on suspended thrombocytes or better on the particles of kaolin. The total time, from the drawing of blood until the focusing on the preparation, was approximately 7 minutes.