484 DIGESTION. 



Sometimes, however, several days are required to convert the 

 whole into peptones. 



Dyspeptone. The dyspeptone of fibrin is a part of the syn- 

 tonin or parapeptone, which becomes insoluble in 2 per cent, 

 hydrochloric acid, and therefore falls as a fine precipitate. It 

 also, according to Meissner, is incapable of further digestion, 

 and only differs from parapeptone in being insoluble in dilute 

 alkalies and dilute acids, and therefore is precipitated sponta- 

 neously from gastric juice without neutralization. 



The dyspeptone of fibrin still requires investigation. The 

 dyspeptone of casein has lately been examined by Hoppe- 

 Seyler and Lubavin ; as it consists partly, at least, of a non- 

 albuminous substance, they consider casein to be composed, 

 like haemoglobin and vitellin, of an albuminous, combined with 

 a non-albuminous, body. 



Metapeptone is merel}' an intermediate stage between syn- 

 tonin and peptone. 



Peptones. There are several kinds of peptones, but they 

 still require further investigation. Meissner distinguishes 

 three sorts, which he names a, 6, and c peptones ; c is the 

 final product, the others being probably only preliminary 

 stages in its production ; a is precipitated from neutral solu- 

 tions by concentrated nitric acid, and from solutions slightly 

 acidulated with acetic acid by potassium ferrocyanide ; b is 

 not precipitated by concentrated nitric acid, but is precipitated 

 by acetic acid and potassium ferrocyanide; c is not precipitated 

 by either of these reagents. 



** 117. Demonstration of the Digestive Action of 

 Pepsin. Take three test-tubes, and put into the first, water 

 with a few drops of glycerin extract of pepsin ; into the second, 

 0.1 per cent, hydrochloric acid; and into the third, the same 

 acid with a few drops of the glycerin extract. Throw into 

 each a small piece of fibrin, taking great care to choose pieces 

 not only of the same size, but of the same texture, as hard 

 pieces are much more slowly acted on either by acid or by 

 gastric juice. Label each, or note the number of the hole in 

 the rack in which each is placed, and put them all in the water- 

 bath at 40 C. (fig. 331). In order to obtain a sufficient 

 quantity of solution of peptones for testing, is is desirable at 

 the same time to put a larger quantity of fibrin in a beaker 

 with dilute acid, and when it has swollen up and become 

 transparent, add some glycerin extract to it, and place it with 

 the ivst. Look at the test-tubes again in five minutes or so, 

 and if the pepsin extract is strong, the bit of fibrin in the gas- 

 tric juice will be partly dissolved, while the one in the acid 

 will have swollen and become translucent, still retaining its 

 form, while that in pepsin alone will be unchanged. Filter 

 the artificial gastric juice from the residue of fibrin. Put a 



