Chcmico-Physiological liesearcJies. 317 



The following observations indicate that albumen may 

 change back again into fibrine by a continuation of the me- 

 tamorphosis by which fibrine is changed into albumen. A 

 solution of venous fibrine in saltpetre liquor was left in a tall 

 glass for fourteen days ; it became turbid at the top, and this 

 extended downwards and increased in quantity : the white 

 matter which thus separated was fibrine in its arterial state, 

 insoluble in the saltpetre liquor. 



This change appears to take place also in blood : venous 

 blood being received in a solution of Glauber's salt, it re- 

 mained without coagulation for six or eight hours ; but after 

 that, a colourless, nearly transparent coagulum, two inches 

 thick, formed on the surface. When this was removed, an- 

 other gradually formed, and this formation of fibrine on the 

 surface of the liquid blood could be very often repeated. 



Oxygen does not exert the same action on albumen of the 

 blood or of eggs as upon fibrine ; but if uncoagulated albu- 

 men, prepared by the spontaneous drying of serum, be washed 

 with water, to remove its saline constituents, the residual 

 portion, which becomes then insoluble in water, acts on oxy- 

 gen as fibrine does, absorbing it and evolving carbonic acid. 



The water with which the albumen had been washed, con- 

 tains all the salts and free alkali, besides a quantity of or- 

 ganic matter which has the properties of casein. During its 

 evaporation a skin forms on its surface as upon milk, and it 

 is not at all coagulated by boiling. On incineration it leaves 

 a strongly alkaline ash with much common salt. 



The albumen of serum may be totally changed into this 

 caseous form by the addition of free alkali, in such proportion 

 that the liquor slightly browns turmeric paper ; it then does 

 not coagulate by heat, but forms a pellicle, which is renewed 

 as often as removed, just as with milk. That the composition 

 of this pellicle is identical with that of casein, results from the 

 following analyses: — 



I. 0"259 of milk pellicle gave, by combustion with chro- 

 mate of lead, 0'524' carbonic acid, and 0*179 water. 



II. 0'289 of the same gave 0'593 of carbonic acid, and 

 0*200 of water. 



III. 0-177 gave 0*360 carbonic acid, and 0*120 of water. 

 0-233 of the pellicle of blood serum warmed with free 



alkali, gave 0*4'70 carbonic acid, and 0*162 of water. 



0*178 of milk pellicle gave by the method of Will and 

 Varrentrupp, 0*44'5 of chloride of platina and ammonium. 



0*212 of tiie serum pellicle gave by the same method 0*522 

 of the chloride of platina and ammonium. 



Hence the milk pellicle contains in 100 parts, 



