CHAP. IL] MEISSXER'S RESEARCHES. 115 



which he obtained, a brief resume of his chief conclusions appears 

 desirable 1 . 



Para e t ne term was applied by Meissner to the neutral- 



isation precipitate obtained when the product of diges- 

 tion of a proteid by natural or artificial gastric juice is so nearly 

 neutralised that only a faint acid reaction persists. Under these 

 circumstances there falls a white flocculent precipitate, composed of 

 the body to which Meissner ascribed the name of parapeptone. He 

 described it as a body insoluble in pure water, but easily soluble in 

 the weakest solutions of acids and alkalies, and precipitated from its 

 solutions by the addition of sodium or potassium chloride. Para- 

 peptone has been usually but incorrectly spoken of as identical with 

 acid albumin or syntonin. It is identical with the body to which 

 Kiihne has assigned the name of antialbumat (see p. 121). In what 

 respect, it will be asked, does parapeptone or antialbumat differ 

 from syntonin or acid albumin ? Apparently in the fact that whilst 

 the latter body can readily be digested by pepsin and an acid, para- 

 peptone is unacted upon by them. This remarkable property of 

 undigestibility was pointed out by Meissner himself as distinguishing 

 parapeptone from acid albumin. A further distinguishing property 

 was pointed out by Meissner, to wit, that when a solution of syntonin 

 is nearly neutralised and pure alcohol is added, this throws down a 

 precipitate. Under exactly similar circumstances a solution contain- 

 ing parapeptone is not precipitated. If the alcohol, however, con- 

 tains ether, parapeptone is thrown down. 



, . On adding a little more acid to the liquid from 



Metapeptone. , . , & J , . ., ,^ ,.. . 



which 'parapeptone has been precipitated, Meissner 



obtained occasionally a further, though scantier, precipitate, separable 

 by filtration, and insoluble in very dilute acids (O'l per cent.) though 

 soluble in stronger acids. This body Meissner termed ' metapeptone,' 

 and looked upon also as an end-product. 



Peptones In the filtrate from which parapeptone and meta- 



a, p and y. peptone had been separated, Meissner distinguished 



three separate soluble bodies, which he classed together in the group 



of peptones, but which he found to differ somewhat in their re- 



actions. 



Peptone a, precipitable by concentrated nitric acid as well as by 

 potassium ferrocyanide and dilute acetic acid. 



Peptone 0, not precipitated by nitric acid, but by potassium 

 ferrocyanide and strong acetic acid. 



Peptone 7, not precipitated by nitric acid, nor by acetic acid and 

 potassium ferrocyanide. 



We now know that Meissner's peptones a and /3 were bodies 



1 Meissner, Zeitschrift fur rat. Med. Bd. vu. vm. x. and xiv. 



82 



