tiLYCOCKN AND FAT. 171 



it wii.N 196.2 . The sjniie uj»i>Ht*s tt) the telMpemtuie at which 

 the iixliiie stailiilijr tli-S!ijtpeius ; in the mse «if ;rl_vt*<>^eli fmijj yeast 

 u teiiijieiatme nf 72 1** 73 C is ie<jiiiieil, whilst hi thut fioui other 

 fun^i(such jis Boietus ft/u/i'^,«tc.), decoloiution ooeurs at 58" to6o' C. 

 Theie i> !ihv:i\s the ptx>v>iliility of having; to reekiai witli the 

 exi>tein.e of >evei-:il isoiiieiic glycogeus, ill re^rd to which .*>ee 

 an observation by K. Bhaix (I.). 



The qiiatititittive ileteiuiiuation of the plyco^ien content by 

 the Kiielz n»etho«l— which, as nHHlifie<l by E. Pkheuek (II.), fur- 

 nishes ieli;il>le results — is a Very troubles^aue task. L'Liut]i;iu 

 worke<I out a coloiiuietric method, tlie chief features of which 

 con.sist in <lissulviut; out the »rlyc«^'^en fixmi a wt- i^he<l (dry ) 

 siiuiple, by re[»eate<l extniction with alkaline water, then eon- 

 vertinj; the same into its brown ioiline i-oujj>ound, and tinally 

 estimating the aniouut by compaiing the colour with that 

 obtained In ajijilying the sjiuie treatment to a i;lyeo«ren solution 

 of known streu'rth. In this manner he ol»taiue<l the following 

 figures, referretl tt> dry resitlue : 20 per cent, of glycogen in a 

 sample of liohtua etiulia ; 14 per cent, in a sample of Amanita 

 »/,'■ ■ •. and 51 per cent, in a sjimple of yeast. This la.^t 

 fi;. - 1 ees with that obtained seveml yeai-s earlier in a different 



manner by E. L.xikent (VIII.). whti found that the riche.st of 

 seveml yeast samples containeil alx)Ut 32.6 per cent, of 

 glycogen. 



On the instigation of I^ Erkeka (VII.), LAurent al.so en- 

 deavoured to investigjite the conditit>ns favouring the enrich- 

 ment of vea.^t cells in glycogen, and found that, fi^r this purjxise. 

 the metliod of culture on wort gelatin is particulaily useful. 

 The following substances were recognised as glycogen formers : 

 lactic acid, succinic acid, malic acid, aspanigin. glutamine, e^^ 

 albumin, peptone, numnite, glucose, hevuh»se. saccharokse. and 

 maltose. Acconling to M. Chemek (1.), the.se mu.st be supple- 

 mented by (/ pilacto.se and </-mannose; but, on the other Iiand, 

 he found anU)ino.se. rhaninose, st)rl>o.se, as well as lactovSt» and 

 glycerin, to be unsuitable; though a contrary opinion with 

 regartl to the two last was expressed by E. Ljiurent. E. Kaysek 

 and E. lioiLLAXOEu (l.)then inve.stigateil the influence of other 

 conditions, e.ij. the presence of air, and the percentage content, of 

 tartaric acid, malic acid, or citiic acid, on the inception an»l 

 progress of glycogen enrichment. In twenty-eight st<.K"ks of 

 wine yeJtst examined with this object. Hi< hahd Meissxek (111.) 

 found that glycogen makes it.s appeaiance, even in the young 

 buds, when the latter have attaine*! aKnit one-fifth the diameter 

 of the jvu-ent-cell. A notable obser\iition. and one worthy of 

 further investigation, was made by M. Ckemer (VI.). n.imely. 

 that the ;;lvco:;en reaction tK-cumnl in alH>ut twelve hours in a 

 glycogen-free presseil yeast juice that had been treatetl with 

 10 per cent or more of fermentable sup\r (dextnxse) and kept at 



