Page:Proceedings of the Royal Society of London Vol 60.djvu/373

346 but is precipitated by salicylsulphonic acid, and the precipitate coagulates on heating. It behaves with neutral salts and salts of the heavy metals similarly to the previously described substances. It does not cause intravascular coagulation of the blood when intravenously injected into dogs or pigmented rabbits, neither will the very slow injection of minute quantities into the circulation of dogs indace a “negative phase.” It does not induce coagulation when added to 1 per cent, sodium carbonate plasma.

Colloid £ is prepared in a similar manner to the colloid hypoxanthine being substituted for xanthine. It has a similar appearance to the colloid e, is laevorotatory (aD = —40), gives Millon’s reaction, and negative results with the other tests characteristic of proteids.

It also behaves with neutral salts and salts of the heavy metals in a similar manner to the previously described substances. When intravenously injected into the circulation of dogs or pigmented rabbits, it fails to induce intravascular coagulation, neither will it cause coagulation when added to extravascular 1 per cent, sodium carbonate plasma.

Colloid rj.-—The colloid y is prepared by the interaction of tyrosine and phosphorus pentoxide for three hours at 130° C. in sealed tubes. The product of this reaction is a pinkish friable powder, sparingly soluble in cold water and soluble on boiling. This substance does not yield Millon’s reaction. After washing in cold water to remove the contaminating phosphoric acid, the powder is dissolved in concentrated ammonia, and a straw-coloured opalescent solution is obtained. This is evaporated down vacuo, and the resulting substance appears as a number of plates, similar in appearance to those of the previously described colloids, and which are soluble in warm water, giving an opalescent solution. This solution is precipitated by salicylsulphonic acid and the precipitate coagulates on heating. It is also precipitated by salts of the heavy metals, and separated from solution by neutral salts. It does not yield any of the distinctive colour reactions of proteids, and fails to produce intravascular coagulation when intravenously injected into rabbits.

The method of differentiating the members of a mixture of proteids by fractional heat coagulation was introduced by Halliburton,* and employed by him more especially in the examination of the proteids of serum. This method was subsequently used by Corin and Berardf in separating the albumins of the white of egg, and by Chittenden

f Corin and Berard, ‘ Bui. de l’Acad. Boy. de Belgique,’ vol. 15, 4, 1888.
 * Halliburton, ‘ Journ. Physiol.,’ vol. 5, p. 159.