346 Dr. J. \Y. Pickering. The Chemical and Physiological 



but is precipitated by salicylsulphonic acid, and the precipitate coagu- 

 lates on heating. It behaves with neutral salts and salts of the heavy 

 metals similarly to the previously described substances. It does not 

 cause intravasculiir 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 induce 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 e, hypo- 

 xanthine being substituted for xanthine. It has a similar appear- 

 ance to the colloid e, is leevorotatory (a D = 40), gives Milloii'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 i). The colloid if 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 sub- 

 stance 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 in vacuo, and the resulting sub- 

 stance 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 1 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 coagu- 

 lation when intravenously injected into rabbits. 



II. The Fractional Heat Coagulation of Synthesised Colloids. 



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 Coriii and Berardf 

 in separating the albumins of the white of egg, and by Chittenden 



* Halliburton, ' Journ. Physiol.,' TO!. 5, p. 159. 



f Corin and Berard, ' Bui. de 1'Acad. Boy. de Belgique,' vol. 15, 4, 188S. 



