CHEMISTRY OF THE YEAST CELL NLTLEL'S. lOi 



air-puiin), furmed a wliite iiml tairly pure {ji-e[Mimtion. Aim- 

 lo;j;ous substjinces have been se|jjinite(l fioui the most divergent 

 animal and vegetable organs, and classilied under the collective 

 term nudeins. 



The lir>t investigations concerning the percentage projxjrtion 

 of nuclein to the tobil nitrogenous constituents of ye^ist were 

 pi-rformed by A. Sii rzKit (1.). According to this worker, the 

 dried resiilue obtained from beer yeast bv several days' cold 

 exti'action with 95 per cent, alcohol followed by drying over 

 sulphuric acid, contained 8.65 per cent, of totjil nitrogen, of 

 which 2.26 per cent. ((»r more than a (juarter) was in the form 

 of nuclein. Still richer in this respect was the thallus of a 

 mould fungus of undetermined species, which settled fron» the 

 air into a nutrient solution containing t;irtaric acid ; since, out 

 of 3.7S per cent, of total nitrogen in the dry residue, 1.54 per cent, 

 (or nearly 41 per cent, of the whole) was present as nuclein. 



It is to the labours of A. Kossel and his pupils that we 

 are mainly indel>te«l for information on the chemical constitution 

 of nuclein in general, and of yeast nuclein in particular. Their 

 discoveries furnished the basis for Kossel's (II.) clas.sification 

 of the nucleins into two groups. The fiist includes substances, 

 which, so far as is known, do not occur in cell luuhi. a!id which 

 were named paranucleins by Kossel, or pseudonucleins by Ham- 

 MAUSTE.v (ill.). When decomposed by dilute acids they > ield 

 only phosphoric acid and all)umin. On the othei- hand, under 

 the .same treatment, the true nucleins, which alone form the 

 subject of the following lines, furnish, in addition, basic sub- 

 .stances to which the name nuclein bases has been given. 



An import4int elucidation of the constitution of nuclein wa.s 

 first presented by li. Ai.i.Man.n (I.) by the discovery that the.se 

 proteids are decomposed by dilute alkalis intt^ albumin an<l a 

 nitrogenous aciil, riili in jtiiosphorus, which has received the 

 name of nucleic acid. Tliis therefore is the prosthetic side 

 chain in the nuclein complex ; and it genenilly receives an 

 additional appellation indiwitive of the origin of the nuclein in 

 ipiestion. All tlie varieties of nucleic acid exhibit the character- 

 istic behaviour, when he^ited with dilute acids, that they sulYer 

 decomposition into one or other of the nuclein bji.ses described 

 lielow. The molecule of nucleic acid is composed of a large 

 nuiuber of atoms. Those of phosphmus and nitiogen .stand in 

 the ratio i : 3 in nearly all the instiinces known. So far, only 

 two exceptions to this rule have been observed. One of them 

 is the giianylic acid, isolated from the nuclein proteid oi the 

 j)ancreas of the ox and more closely examineil by 1. Bangs (1.). 

 the molecule of which acid contains 5 atoms of nitrogen to eivch 

 atom of phosphorus. The other is a nucleic acid isolated from 

 the embryo of wheat by Tn. li. OsuoitXE and (,J. F. C'ampiieli. 

 (I.), the iiitio P : N being in this ca.se 1 : 4. 



vol.. II. L 



