The structure of the natural anticoagulant, heparin, is gradually being elucidated. As each step forward is made, attempts to synthesize molecules with the biological activity of heparin receive renewed impetus. It is now known (Jorpes, 1939) that heparin is composed of glucuronic acid and glucosamine though the mode of linkage of these two parts is not yet clear. Some of the hydroxyl groups of these components are esterifiedwith sulphuric acidbut the exact distribution of sulphate groups is uncertain. Recently, however, Jorpes, Bostrom & Mutt (1950) have shown that during the weak acid hydrolysis of heparin, sulphuric acid appears at the same time and with the same rate as amino groups, leading to the view that the amino group is combined with

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Summary: To clarify tthe mechanism by which local application of silver compounds protects burns against infection, an ion-specific electrode was used to measure the concentration of silver ions in solutions. By this method it was shown that in burn dressings silver ions were reduced to a very low level by precipitation as silver chloride. The antibacterial effect was found to depend on the availability of silver ions from solution in contact with precipitate. Between 10-5 and 10-molar silver nitrate solution in water was rapidly bactericidal. The minimal amount of silver nitrate causing inhibition of respiration of skin in tissue culture was about 25 times the minimal concentration of silver nitrate that inhibited growth of Pseudomonas aeruginosa.

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Several well-known anticoagulants are in use for blood sample tubes, each having some special application, but there is little doubt that the naturally occurring anticoagulant, heparin, would find wider application were it not so difficult to prepare and consequently expensive. Chemically prepared sulphuric esters of polysaccharides are known to have anticoagulant action. One of these, dextran sulphate, has recently been prepared (Ricketts, 1952) in a form suitable for therapeutic use (Walton, 1951 In the field of haematology the requirements of an anticoagulant are somewhat more critical. It was quickly established that there was no effect on the haematocrit determination, but there appears to be a slight though probably negligible effect on the erythrocyte sedimentation rate. Walton (1951) reports that the ordinary haematological determinations, haemoglobin, red cell and white cell counts, are not interfered with.In the field of physiological research there appears to be scope for an anticoagulant of the heparin type in experiments involving the perfusion of tissue with blood. Since it is not prepared from tissue, dextran sulphate is not contaminated with pharmacologically active substances, e.g., histamine. No doubt other specialized applications will suggest themselves to the research workers concerned. Where a sodium salt is unsuitable it is a comparatively simple matter to exchange the sodium for hydrogen by passage through a column of ion exchange resin. The acid solution of dextran sulphate may then be neutralized with any selected base.

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