322 CHEMISTRY OF THE PROTEIDS CHAP. 



lower temperature than is the other. Subsequently fractional heat- 

 coagulation has been chiefly employed by Fredericq l and Halliburton 2 

 and his pupils for the isolation and characterisation of individual 

 albumins. They found the coagulation-temperature to be very con- 

 stant, and to differ only 1 to 2. Generally speaking, it has been 

 found that the complex, tissue -forming albumins and the more 

 differentiated bodies, such as fibrinogen and myosin, coagulate at a 

 lower temperature than do the simple albumins and globulins. The 

 coagulation-temperature of each albumin, as far as it has been deter- 

 mined, will be given when dealing with the individual albumins. 



If the reaction be alkaline we are dealing with much more com- 

 plicated conditions. Pauli 3 finds that most salts lower the coagulation- 

 temperature if they be present in low concentrations, while they raise 

 it in higher concentrations ; and further, that the ions of the salts act, 

 as is usual, collectively. No further definite facts could be ascertained 

 as regards salting-out and similar processes. 



That egg-white diluted with nine times its bulk of water does not 

 coagulate was first observed in 1880 by William Eoberts. 4 



10. The Formation of Additive Compounds 



This question is fully discussed in the author's Physiological 

 Histology, pp. 68-70. It will suffice here to point out that the two 

 reagents chiefly used by the author were the aldehydes, which give 

 rise to methylene-compounds, see this book p. 250, and secondly 

 osmium tetroxide, which acts as an oxidiser. Neither aldehydes 

 nor osmium tetroxide are electrolytes, and whenever they have to 

 be used for fixing the morphological appearance of cell-albumins, they 

 should always be made up in normal, i.e. isotonic salt solutions. 



Attention is drawn to the article by Neubauer, 5 who along with 

 Langstein has found that all substances with a double or treble link 

 between two carbon-atoms will reduce osmium tetroxide, which there- 

 fore is a reagent for unsatisfied compounds. The same conclusion 



1 L. Fredericq, 'Coagulation du sang,' Bull. d. VAcadZmie royale de Belgique, 

 2 Ser., Bd. 64. (1877), 7 Juli ; also Ann. de Soc. de Medecine de Gant. (1877); 

 Berard andCorin, Travauxdu laboratoire, etc., de Fredericq If. 171 (1887); L. Frtdericq, 

 Zentralbl.f. Physiolog. 3. 601 (1890). 



2 W. D. Halliburton, Journ. of Physiol. 5. 155 ; 8. 133 (1887) ; 11. 454 ; R. 0. 

 Hewlett, ibid. 13. 493 (1892). 



3 W. Pauli, Pftiiger's Arch.f. d. ges. Physiol. 78. 315 (1899). 



4 William Roberts, Lumleian Lectures on Digestive Ferments and Artificially 

 Digested Food (London : Smith, Elder and Co., 1880). 



5 Neubauer, Sitzber. d. MuncJiener morphol. -physiol. Ges. 19. 31 (1905). 



