100 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



Any of the coagulated proteids may be converted into acid albumen 

 through solution in the mineral acids. If a solution of albumen is 

 gently heated to boiling with dilute hydrochloric acid, no coagulum will 

 be formed, from the fact that in the gradual elevation of temperature the 

 albumen in solution has had time to be converted quickly into acid 

 albumen through the action of the acid. If, now, a small quantity of a 

 concentrated mineral acid, especially hydrochloric, be added, an abundant 

 precipitate will form, and this precipitate is soluble in an excess of 

 mineral acid, especially if subjected to heat. 



It is thus shown that acid albumen is soluble in concentrated mineral 

 acids. It is insoluble in them when they are moderately concentrated, 

 and it is soluble again when they are very dilute. Egg-albumen, in 

 certain respects, differs from serum-albumen in its behavior to dilute 

 acids. If dry serum-albumen is dissolved in a concentrated mineral 

 acid, it is readily converted in its process of solution into acid albumen. 

 If this solution of serum-albumen in concentrated acid is then diluted 

 with twice its volume of water, acid albumen will be precipitated, and if 

 the precipitate is filtered off it may readily be dissolved in water, from 

 the fact that it still holds clinging to it enough acid to make a dilute 

 acid solution. Therefore, it is not a solution of acid albumen in water, 

 but in dilute acid. Egg-albumen is less soluble in concentrated nitric 

 acid or hydrochloric acid, and when precipitated from such a solution it 

 is less readily dissolved in water. 



Fibrin also is soluble in concentrated mineral acids, and is rapidly 

 converted into syntonin ; therefore, it may be said that all proteids are' 

 capable of being converted into derived albumens. 



Syntonin, dissolved in dilute hydrochloric acid, rotates the plane of 

 yellow light — 12° to the left, and this degree of rotation is independent of 

 the concentration of the solution, but may be increased to — 84.8° if the 

 solution is heated. Syntonin contains sulphur, as may be readily shown 

 by dissolving some syntonin in liquor potassa;, and adding a solution of 

 lead acetate and boiling ; the fluid will then become brown from the 

 formation of lead sulphide. When precipitated from its solutions by 

 neutralization acid albumen forms a white, gelatinous substance insoluble 

 in water and sodium chloride solutions, but soluble in lime-water (in 

 which solution, as already stated, it undergoes partial coagulation when 

 boiled) , and in dilute acids and alkaline solutions. If, to the solution in 

 lime-water, after having undergone partial coagulation through boiling, 

 magnesium sulphate be added, a still further precipitation will be caused. 

 Cold solutions of acid albumen are not precipitated by magnesium sul- 

 phate, even if the acid albumen be dissolved in an alkaline solution. If, 

 however, the solution of acid albumen and alkali be warmed, it is then 

 precipitated by the addition of magnesium sulphate or calcium chloride, 



