428 OHEMISTBT OF THE LEUCOMAINS. 



lated. The liquid is then freed from acid by baryta and from the latter by 

 carbonic acid, after which it is neutralized with nitric acid and evaporated. 

 When dried in a vacuum it can be weighed as the neutral nitrate CgS-u 

 NiOj.HNOa + }H,0. The arginin may also be estimated polarimetrically, 

 or as the acid di-nitrate. 



The lysin is contained in the original filtrate from the histidin and 

 arginin silver precipitate. To isolate it, the solution is acidulated and the 

 silver removed with hydrogen sulphid. The combined filtrate and wash- 

 water is concentrated to about 500 c.c, and after sulphuric acid is added 

 to make a 5 per cent, solution it is precipitated with phosphotungstic 

 acid. The precipitate is thoroughly washed. It contains most of the 

 lysin and a small amount of mono-amido acids. The bulk of the latter is 

 contained in the filtrate. The precipitate is decomposed with baryta and 

 filtered. The combined filtrate after removal of excess of barium with 

 carbonic acid is evaporated to dryness. The residue is taken up in water, 

 filtered, and the filtrate is again evaporated to dryness. The residue is 

 now taken up in alcohol and an alcoholic picric acid solution is added, 

 carefully avoiding an excess. The precipitate is filtered ofi^, washed with 

 a little absolute alcohol and then is dissolved in boiling water. The solu- 

 tion after concentration and cooling yields needle-shaped crystals which 

 are filtered off", washed and weighed as lysin picrate. Some lysin remains 

 in the mother liquors. 



Instead of decomposing the phosphotungstic acid precipitates with baryta 

 Winterstein advises extraction with ether and hydrochloric acid (Z. P. C. , 

 34, 154). 



It should be noted in this connection that the amount of lysin and oi 

 ammonia in proteid cleavage depends upon the amount of salt present. 

 When salt is present the nitrogenous humin substances are decreased and 

 the yield of lysin and ammonia is increased (Hart, Z. P. C, 33, 347). 



PROTAMINS AND HISTONS. 



By far the most fruitful result of the study of the hexon bases is 

 the light which has been shed upon the composition of the proteids. 

 Moreover a better insight has been gained into the nitrogen metab- 

 olism of the body. The fact that arginin on hydration with baryta 

 yields urea indicates the existence of a urea or rather guanidin group 

 in that base and hence in every proteid. From the constitution of 

 arginin and lysin (p. 437, 444) it will be seen that these represent 

 respectively diamidovalerianic and diamidocaproic acids. It is by the 

 cleavage of these acids that bacteria (and enzymes, Lawrow) yield 

 the well known ptomaiins cadaverin and putrescin. The presence of 

 these ptomains in cystinuria is now more readily understood. The 

 monamido acids represented by leucin, tyrosin, asparaginic acid and 

 phenyl alanin, make up a third type of nitrogen combination in the 

 proteid molecule. The liberation of ammonia by hydrolytic change^ 

 as seen in the table on p. 426, indicates the existence of a fourth as 

 yet unknown nitrogen group. The bulk of the proteid nitrogen is 

 therefore found in the four groups mentioned. The fact that am- 

 monia and amido acids are changed in the body into urea, when 

 applied to the proteid molecule as thus understood, readily explains 

 the transformation of the greater part of the nitrogen of our food 

 into the final waste product, urea. 



