42 PROTEIDS. 



first noticed and isolated by Meissner under the name of a-peptone, is 

 identical with Bence-Jones' proteid in the urine of osteomalacia, and 

 has also been known under the name of ' propeptone.' Of late years it 

 has been recognised as occurring not infrequently in urine 1 , and it is 

 more than probable that many of the older statements as to the 

 occurrence of peptones in urine and other fluids referred really to the 

 occurrence of hemialbumose. It is also stated to occur normally in 

 the marrow of bones 2 , and in cerebrospinal fluid 3 . Since it is readily 

 peptonised by trypsin with the simultaneous formation from the 

 peptone of much leucin and tyrosin, hemialbumose scarcely makes its 

 appearance in any appreciable quantity in the final products of a 

 pancreatic digestion. It is best prepared by the action of a small 

 amount of very active pepsin on a considerable mass of fibrin, previously 

 swelled up into a gelatinous mass by the action of '2 p.c. HC1 at 40 4 . 

 Under the action of the pepsin the fibrin liquefies : as soon as this is 

 complete, dilute sodium carbonate is added until the reaction is just 

 faintly alkaline, by which means a bulky precipitate is obtained. This 

 is removed by filtration and the filtrate now contains a large amount 

 of hemialbumose and but little peptone, and may be utilised directly 

 for the tests characteristic of the albumose. 



Preparation of pure hemialbumose (Salkowski) 5 . Acidulate the 

 filtrate described above strongly with acetic acid, add an excess (37 '5 

 grms. to each 100 c.c.) of sodium chloride, and agitate the mixture 

 until it is saturated with salt. The hemialbumose is thus precipitated ; 

 it is now collected on a filter, washed with saturated solution of sodium 

 chloride, dissolved again in water and reprecipitated by acetic acid and 

 sodium chloride. This process is repeated and the final prpduct is 

 then dissolved in a minimal amount of water and freed from salt by 

 dialysis 6 . It may then be concentrated, precipitated by alcohol and 

 dried, first over sulphuric acid and then at 105. 



Reactions of hemialbumose. The pure dry substance is not readily 

 soluble in distilled water, but readily soluble in traces of acids, alkalis 

 and neutral salts (sodium chloride). These solutions give the following 

 characteristic reactions : 



1. Acidulate fairly strongly with acetic acid and add a few drops 

 of saturated solution of sodium chloride ; a precipitate is formed which 



1 Salkowski u. Leube, ' Die Lehre von Harn.' 1882, Sn. 210, 350. 



2 Fleischer, Virchow's Arch. Bd. 81, (1880), S. 188. 



3 Halliburton, Jl. of Physiol Vol. x. (1889), p. 232. 



4 For precise details see Zt. f. Biol. Bd. xix. (1883) S. 184. See also Drechsel, 

 " Anleitung zur Darstell. physiol.-chem. Praparate." Wiesbaden, 1889, S. 23. 



5 Virchow's Arch. Bd. LXXXI. (1880), S. 552. 



6 During the dialysis some loss of albumoses occurs, since they are slightly 

 diffusible, but less so than the peptones. Zt. f. Biol. Bd. xx. (1884) Note on p. 27. 



