APR] CHEMICAL BASIS OF THE ANIMAL BODY. 705 



in neutral saline solutions, such as those of sodic chloride, that it 

 is readily soluble in dilute acids or dilute alkalis, and that its solutions 

 in acids or alkalis are not coagulated by boiling. When suspended, in 

 the undissolved state, in water, and heated to 70 C, it becomes coagulated, 

 and is then undistinguishable from coagulated serum-albumin, or indeed 

 from any other form of coagulated proteid. It is evident that the sub- 

 stance when in solution in a dilute acid is in a different condition from 

 that in which it is when precipitated by neutralisation. If a quantity 

 of serum- or egg-albumin be treated with dilute hydrochloric acid, it 

 will be found that the conversion of the native albumin into acid- 

 albumin is gradual ; a specimen heated to 70 C immediately after the 

 addition of the dilute acid, will coagulate almost as usual ; and another 

 specimen taken at the same time will give hardly any precipitate on 

 neutralisation. 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 neutralisation 

 precipitate will be considerable. Still later the coagulation will be absent, 

 and the whole of the proteid will be thrown down on neutralisation. 



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

 removed by repeated washing, be treated for some time with dilute 

 (2 per cent.) hydrochloric acid, the greater part of the muscle is dis- 

 solved. The transparent acid filtrate contains a large quantity of 

 proteid material in a form which, in its general characters at least, 

 agrees with acid-albumin. The acid solution of the proteid is not 

 coagulated by boiling, but the whole of the proteid is precipitated on 

 neutralisation ; and the precipitate,, insoluble in neutral sodic chloride 

 solutions, is readily dissolved by even dilute acids or alkalis. The 

 proteid thus obtained from muscle has been called syntonin, but we 

 have at present no satisfactory test to distinguish the acid-albumin (or 

 syntonin) prepared from muscle from that prepared from egg- or serum- 

 albumin. When coagulated albumin or other coagulated proteid or 

 fibrin is dissolved in strong acids r 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 dis- 

 tinguished from acid-albumin prepared 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 alkalis, but 

 also in dilute solutions of alkaline carbonates ; its solutions in these are 

 not coagulated by boiling. 



If sodic chloride in excess is added to an acid solution of acid- 

 albumin, the acid-albumin is precipitated : this also occurs on adding 

 sodic acetate or phosphate. 



F. 45 



