Page:Proceedings of the Royal Society of London Vol 60.djvu/369

342 dogs, it is found not to induce intravascular coagulation, although its chemical and physical characteristics are apparently unchanged. This result shows that the chemical reactions used for “ testing ” proteids are not sufficiently delicate to indicate the chemical changes which are demonstrable by physiological methods. The following experiment illustrates this result:—

Experiment 6 —Black rabbit (weight 7 lbs. 9 oz?.) ; anaesthetic, chloroform and ether; 120 c.c. of redissolved solution injected produced dyspnoea, exophthalmos, dilatation of pupils. A further injection of 10 c.c. of this substance was immediately fatal. Post-mortem examination failed to reveal any clots in the animal’s vessels. Blood withdrawn from the carotids during the injection showed only one minute’s decrease in the time taken to complete coagulation.

Experiment 7.—In another experiment, where minute quantities of this substance were very slowly injected, there was no retardation of the time of coagulation, like that produced by the original substance or by a nucleo-pnoteid.

Colloid ft.—This substance is formed by heating together tyrosine, biuret, and phosphorus pentachloride in the ratio of equal weights of the two former substances, with twice the weight of the latter, for six hours at 125° to 130° C. in sealed tubes. The product of this reaction is a grey powder insoluble in cold water, and very sparingly soluble on heating. This substance gives the xantho-proteic and Frohde’s reaction, but fails to give typical colour reactions with the other reagents commonly used in testing proteids. It should be repeatedly washed until all traces of the contaminating phosphoric acid are removed, and then dried in vacuo at about 30° C. It readily dissolves in concentrated ammonium hydrate, and the solution is opalescent and laevorotatory (aD = —48), and in appearance indistinguishable from that of the other colloids produced. It gives the following distinctive reactions as classified in the annexed table, but does not digest when subjected to the action of either pepsin and 0 2 per cent, hydrochloric acid for three days at 38° CL,-or of an alkaline solution of trypsin, kept at the same temperature for a. similar time. It yields the following distinctive reactions

Colloid ft. CuS04 KHO. CoS04 KHO. NiS04 KHO. H2S04 and molybdic acid. Millon's reagent. HNO, and NH4OH (heating). Saiicyl sulphonic acid. Violetcoloured solution. Heliotrope purplecoloured solution. Faint yellowcoloured solution. Dart blue precipitate. Dart red precipitate. Orange precipitate. Precipitate which coagulates on heating.