340 CHEMISTRY OF THE PROTEIDS CHAP. 



presence of salt, which occurs slowly in the cold, and quickly on 

 heating. The smaller the amount of salt which is present, the 

 more transparent, but also the less firm, is the jelly, and vice vena. 

 Acid-albumin requires for its gelation less salt than does an alkali-albu- 

 minate. Warmth hastens and augments jelly-formation enormously. 



A hard-boiled egg is a good example of the formation of a jelly- 

 like alkali - albuminate, for egg - white is a concentrated alkaline 

 albumin-solution. In the hen's egg, and in the eggs of birds which 

 leave their nests as soon as they are hatched, the alkali-albuminate 

 becomes white and opaque on boiling, while in the eggs of all birds 

 which remain for a considerable time in their nests, as is the case 

 with the crow, the swallow, and the lapwing, the egg-white solidifies 

 on boiling into a jelly as clear as glass, as has been pointed out by 

 Lieberkiihn, Tarchanoff, 1 who introduced the term Tata-albumin, in 

 memory of a little Eussian girl Tata, who observed that swallows' 

 oggs remained clear on boiling, and Helbig. 2 This phenomenon 

 depends on the different amounts of salt and of alkali which are 

 present in the egg-white. The white of hens' eggs may also be made 

 to solidify into a clear jelly by placing the eggs for two to three 

 days into 10 per cent KOH solution (Tarchanoff 1 and Zoth 3 ). 

 Another application of the transparent, jellified alkali-albuminate is 

 that which Koch 4 has introduced into bacteriology, for blood-serum 

 solidifies to a fairly transparent jelly on being heated for some time 

 to 65 ; by altering the concentration of the serum, and the time we 

 take to coagulate the serum, it is possible to somewhat influence the 

 mode of coagulation. 1 



Other Methods of Denaturalisation 



Many other causes, in addition to acids and alkalies, will change 

 the normally occurring, colloidal albumin into a denaturalised state. 



Dry Heat. Pure albumin crystals, according to Wichmann, 5 may 

 be heated to 150, but on being heated for some time in their insoluble 

 state, they become less readily digestible by pepsin and by trypsin, 

 according to Smith, 6 Strohmer, 7 and Rotarski ; 8 Laqueur and Sackur, 9 



1 J. Tarchanoff, Pfluger's Arch. f. d. ges. Physiol. 33. 303 (1884) ; 39. 476 and 

 489 (1886). 2 E. Helbig, Arch.f. Hygiene, 8. 475 (1888). 



3 0. Zoth, Sitzungsber. d. Wiener Akad., Math.-natunv. Kl. III. 1OO. 140 (1891). 



4 R. Koch, Mitteil. a. d. Kaiserlichen Gesundheitsamte, 2. 48 (1884). 



5 A. Wichmann, Zeitschr. f. physiol. Chem. 27. 575 (1899). 



6 H. Smith, Zeitschr. f. Biol. 19. 469 (1883). 



7 F. Strohmer, Chem. Zentralbl. 1902, II. 971. 



8 T. Rotarski, Zeitschr. f. physiol. Chem. 38. 552 (1903). 



9 E. Laqueur and 0. Sackur, Hofrndsters Beitrage, 3. 193 (1902). 



