412 CHEMISTRY OF THE PROTEIDS CHAP. 



The A-nucleo-albumin is soluble in 0'9 per cent NaCl and in O'l per 

 cent CaCl. 



Huiskamp. Extract 200 grammes of finely minced calf-thymus 

 free from fat at a low temperature (which is better than the addition 

 of chloroform) with 600 ccm. of water ; filter and centrifugalise the 

 extract to separate the * nucleo-proteid,' which is soluble in calcium 

 chloride solution, from the 'nucleo-histone' which, within certain 

 limits, is not soluble; add to each 100 ccm. of the clear solution, 

 1 ccm. of 10 per cent calcium chloride solution, so that the solution 

 contains 0*1 per cent of calcium chloride. [The author has repeated 

 these experiments with equivalent amounts of barium chloride and 

 finds it answer even better.] Calcium chloride may be added up to 

 0*5 per cent without dissolving much of the precipitate, but the latter 

 completely dissolves in 2 per cent CaCl 2 solution. Centrifugalise 

 off the calcium chloride-precipitate and dissolve it in water with the 

 help of a few drops of dilute ammonia ; filter ; reprecipitate with 

 CaCl 2 ; centrifugalise ; treat precipitate of nucleo-histone for some 

 hours with 100 ccm. of a 0'8 per cent watery solution of HC1, 

 shaking repeatedly, and the ' nuclein ' will remain in the precipitate, 

 while the histone goes into solution. [The insoluble nuclein gives 

 the proteid reactions except the glyoxylic one; it contains large 

 amounts of the purin-bases, especially adenin, and contains phosphorus. 

 It is soluble in dilute ammonia and is reprecipitated by acetic or 

 other acids.] To obtain histone, dialyse the hydrochloric acid extract 

 to remove all traces of HC1 and CaCl 2 , and other salts, as these interfere 

 with the precipitation of the histone by means of ammonia. When the 

 solution is almost neutral precipitate the historic with ammonia. 

 Histone is insoluble in excess of ammonia, but is soluble in excess of 

 NaOH. As histone combines with HC1 it must be a base, and the 

 nuclein-radical to which it is joined in the nucleo-histone must there- 

 fore be acid. 



Huiskamp asks himself the question whether the nucleo-histone 

 precipitated by the calcium chloride is a compound analogous to the 

 casein of milk. Are we dealing with (1) CaCl 2 + nucleo-histone ; or (2) 

 withCa + nucleo-histone; or (3) does the calcium chloride solution simply 

 render the nucleo-histone insoluble ? His answer to these questions is 

 that calcium plays the part of the base, while nucleo-histone represents 

 the acid radical. From this * calcium nucleo-histonate ' the calcium 

 may be removed by 5 per cent acetic acid. That the nucleo-histone is 

 acid he believes is proved by the fact that the reaction of the solution 

 in which it is suspended remains neutral on the addition of ammonia 

 till the whole of the precipitate is dissolved. As free nucleo-histone 



