Page:Proceedings of the Royal Society of London Vol 60.djvu/372

Rh not, like them, produce intravascular coagulation when intravenously injected into pigmented rabbits. Neither will the colloid 7 when introduced into the circulation of dogs, very slowly and in minute quantities, produce a retardation of the coagulation of blood withdrawn from the carotids.

Colloid 0.—The colloid c is formed by heating at 125° C. in sealed tubes for three hours, equal weights of para-amidobenzoic acid and phosphorus pentachloride. The resulting product, a grey friable powder, insoluble in cold water, was, after washing to remove the contaminating phosphoric acid, dissolved in concentrated ammonia, and evaporated down at a low temperature vacuo. The resulting substance appears as a number of translucent yellowish plates, apparently similar to those previously described. They are soluble in warm water, forming an opalescent straw-coloured solution, which is laevorotatory (aD = —42). This solution gives the xantho-proteic and Frohde’s reaction, but fails to give the typical colour reactions of proteid-like substances with salts of copper, cobalt, or nickel and caustic potash; neither does it give the reactions of Millon, Liebermann, or Adamkiewicz. It is not precipitated by salicylsulphonic acid, but it is precipitated by salts of the heavy metals. Neutral salts separate it from solution like the preceding substances. When freed from salts, it does not coagulate on heating, but if a trace of sodium chloride or of another neutral salt be present, it coagulates on heating to 75° C. When intravenously injected into pigmented rabbits, it fails to produce intravascular coagulation, neither does it hasten the coagulability of blood withdrawn from the carotids. It fails to induce a “ negative phase ” in the coagulation of dogs’ blood. This series of results lends additional support to the view that the coagulation of the blood resulting from intravenous injection of the colloid, is due to the interaction of the colloid with the constituents of the plasma, and not to the heavy nature of colloid molecule.

Colloid e.— The colloid e is prepared by heating together equal weights of tyrosine and xanthine with twice their weight of phosphorus pentachloride at 125° C. for three hours. The product of the reaction is a yellowish powder slightly soluble in warm water. After repeated washing in cold water, it is dissolved in concentrated ammonia, and the resulting solution evaporated down at a low temperature. The resulting substance consists of a number of translucent yellowish plates like those previously described. It is readily soluble in warm water, forming a yellowish opalescent solution, which is lsevorotatory (aD = —38).

This solution gives a typical red when heated with Millon’s reagent, which is not due to an excess of tyrosine, since the intermediate product in the preparation of the substance fails to give this reaction. It does not give any other of the distinctive proteid colour reactions,