414 CHEMISTRY OF THE PROTEIDS CHAP. 



adding either lime water or, after the extract had been rendered 

 slightly alkaline by the addition of an alkali, by adding CaCl 2 . The 

 most abundant precipitate is obtained, however, by the addition of 

 very small amounts of acetic acid, for in 1 per cent acetic or in 0'2 

 per cent HC1 the precipitate dissolves again completely. [This 

 agrees with the behaviour of Malengreau's A-nucleo-albumin, and, like 

 the latter, Bang's nucleo- albumin is soluble in 0*9 NaCl and in 0*1 

 CaCl 2 solutions; like Huiskamp's nucleo -albumin and Malengreau's 

 A-nucleo-albumin, it is precipitated by half saturating the thymus 

 extract with ammonium sulphate. The precipitate so obtained does 

 not, however, completely redissolve in distilled water. 



The nucleo-albumins of Huiskamp and Bang have the following 

 percentage composition : 



C H N P Ash 



Huiskamp . 50'09 7'18 16-11 0'97 3vll. 



Bang . . 49-50 6'35 16'15 1-12 2'36. 



This nucleo-albumin is very readily decomposed by treatment with 

 acetic acid or by alkali into two components, one of which is very 

 readily soluble in dilute alkalies, while the other is not. Acting on 

 the acetic acid precipitate with 0'3 per cent HC1, the nucleo-albumin is 

 dissociated (agreement between Malengreau and Bang), the substance 

 extracted by the HC1 is, however, not a histone, as held by Malen- 

 greau, but an acid-albumin, for " all histones form with acids soluble 

 salts possessing a neutral reaction," while the substance extracted by 

 HC1 is precipitated by ammonia even before complete neutralisation is 

 reached. This acid-albumin is precipitated by 20 per cent saturated 

 ammonium sulphate, its nitrogen content is 16 '5 9 per cent and it 

 contains no phosphorus. The residue which remains after extracting 

 the acetic acid precipitate of the nucleo-albumin with 0'3 per cent HC1 

 is a nuclein, containing phosphorus and a pentose. The precipitation 

 limits for ammonium sulphate are for this nuclein also 20. 



The nucleo-histone is prepared from the original 0'9 per cent 

 NaCl extract of the thymus gland, or the latter may be extracted 

 simply with distilled water. The nucleo-histone is precipitated by 

 Huiskamp's method of adding 1 per cent CaCl 2 solution till the amount 

 of this salt equals 0'2, or in very saturated nucleo-histofae solutions 0'3 

 per cent. The precipitate obtained in this way may be extracted 

 directly with 2 per cent NaCl solution, 1 but this extract is not readily 

 filtrated and is therefore apt to putrefy. To facilitate filtration Bang 

 centrifugalises the CaCl 2 precipitate, shakes the latter well up with 



1 Not rendered soluble with ammonia, according to the method of Huiskamp, as 

 ammonia decomposes the nucleo-histone. 



