CHEMICAL BASIS OF THE ANIMAL BODY. 869 



precipitate on neutralization. Some time later, the interval depending on the pro- 

 portion of the acid to the albumin, on temperature, and on other circumstances, 

 the coagulation will be less, and the neutralization precipitate will be considerable. 

 Still later, the coagulation will be absent, and the whole of the proteid will be 

 thrown down on neutralization. 



If finely-chopped muscle, from which the soluble albumins have been removed 

 by repeated washing, be treated for some time with dilute (0.2 per cent.) hydro- 

 chloric acid, the greater part of the muscle is dissolved. The transparent acid 

 filtrate contains a large quantity of proteid material in a form which, in its gen- 

 eral characters at least, agrees with acid-albumin. The acid solution of the pro- 

 teid is not coagulated by boiling, but the whole of the proteid is precipitated on 

 neutralization ; and the precipitate, insoluble in neutral sodic chloride solutions, 

 is readily dissolved by even dilute acids or alkalies. The proteid thus obtained from 

 muscle has been called syntonm, but we have at present no satisfactory test to dis- 

 tinguish the acid-albumin (or syntonin) prepared from muscle from that prepared 

 from egg- or serum-albumin. When coagulated albumin or other coagulated pro- 

 teid or fibrin is dissolved in strong acids, acid-albumin is formed ; and when fibrin 

 or any other proteid is acted upon by gastric juice, acid-albumin is one of the first 

 products ; and these acid-albumins cannot be distinguished from acid-albumin pre- 

 pared from muscle or native albumin. Though hydrochloric acid is perhaps the 

 most convenient acid for forming acid-albumin, other acids may also be used for 

 the purpose of preparing it. Acid-albumin is soluble not only in dilute alkalies, 

 but also in dilute solutions of alkaline carbonates ; its solutions in these are not 

 coagulated by boiling. 



If sodic phosphate in excess is added to an acid solution of acid-albumin, the 

 acid-albumin is precipitated ; this also occurs on adding sodic acetate or phos- 

 phate. 



As special tests of acid- albumin may be given : 1. Partial coagulation of its 

 solution in lime-water on boiling. 2. Further precipitation of the same solution 

 after boiling, on the addition of calcic chloride, magnesic sulphate, or sodic 

 chloride. 



Dissolved in very dilute hydrochloric acid, acid-albumin (syntonin) prepared from 

 muscle possesses a specific laevp-rotatory power of 72 for yellow light, this being 

 independent of the concentration. l On heating the solution in a closed vessel in a 

 water-bath the rotatory power rises to 84. 8. 



The body known as parapeptone, which makes its appearance during the peptic 

 digestion of proteids, is closely allied to the substances just described. 



2. Alkali-albumin. 



If serum- or egg-albumin or washed muscle be treated with dilute alkali instead 

 of with dilute acid, the proteid undergoes a change quite similar to that which was 

 brought about by the acid. The alkaline solution, when the change has become 

 complete, is no longer coagulated by heat, the proteid is wholly precipitated on neu- 

 tralization, and the precipitate, insoluble in water and in neutral sodic chlorine solu- 

 tion, is readily soluble in dilute acids or alkalies. Indeed in a general way it may 

 be said that acid-albumin and alkali-albumin are nothing more than solutions of the 

 same substance in dilute acids and alkalies respectively. When the precipitate 

 obtained by the neutralization of a solution of acid-albumin in dilute acid is dis- 

 solved in a dilute alkali, it may be considered to become alkali-albumin ; and con- 

 versely when the precipitate obtained from an alkali-albumin solution is dissolved in 

 dilute acid, it may be regarded as acid-albumin. 



It is stated ' 2 as a characteristic reaction of this modified or derived albumin that 

 it is not precipitated when its alkaline solutions are neutralized in the presence of 

 alkaline phosphates ; solutions of acid-albumin, on the contrary, are said to be pre- 

 cipitated on neutralization in the presence of alkaline phosphates, and this difference 

 is considered to be a distinguishing feature of the two proteids. But doubt has been 

 cast on this statement, 3 



Alkali-albumin may be prepared by the action not only of dilute alkalies, but 

 also of strong caustic alkalies on native albumins as well as on coagulated albu- 



1 Hoppe-Seyler, Hdb. Phys. Path. Chem. Anal., Ed. iv. (1875), S. 246. 



2 Hoppe-Seyler, loc. cit, S. 245. 



3Soyka. Ptluger's Arch., Bd. xii. (1876), S. 347. 



