148 ANATOMY OF THE YEAST CELL. 



fai' this view is correct, owing to the absence of means for 

 detecting this carbohydrate. Still more undecided is the ques- 

 tion as to the divex'gent chemical composition of the various 

 strata of the membi-ane. That some difference does exist may 

 be deduced from the influence exerted by chromic acid (dilvited 

 with its own volume of water) on the cell membrane, whereby 

 the inner layer is more readily dissolved than the outer, 

 especially in the case of permanent cells. This observation was 

 first made by H. Will, and was afterwards confirmed by Casa- 

 grandi and supplemented by different staining tests. It was 

 probably owing to a similar observation that Nfegeli was led to 

 surmise that the cell membrane in the films of jNIycoderma is 

 cuticularised. 



The hypothesis founded ox\ the microchemical examination of 

 the yeast cell membrane is undeniably supported by the macro- 

 chemical researches of Salkowski (VI.) on the same point. He 

 found that the residue obtained by extracting pressed yeast for 

 half-an-hour (§ 2 5 4) with boiling 3 per cent, caustic potash solution, 

 and amounting to about 3.1 per cent, by weight of the substance 

 taken, was separable into two components — one soluble, the 

 other insoluble — by prolonged boiling in a large volume of 

 water, under a reflux condenser, or in the autoclave at a pressure 

 of 2 to 2 1^ atmospheres. On separating and concentrating the 

 solution, the soluble constituent was precipitated by absolute 

 alcohol, as a white powder exhibiting the rotatory power a^ 

 173.3° ^^ i74-i°- The results of the ultimate analysis indicate 

 the formula C^jH^yO^. On hydrolysis with dilute acids, practi- 

 cally the whole is converted into ri'-glucose. Iodine in potassium 

 iodide gives a powerful brown-red stain, on which account the 

 substance has received the name erythrocellulose. It differs 

 from the somewhat analogous glycogens in its lower rotatory 

 power. The other constituent of the original residue remains 

 in the form of a colourless jelly at the bottom of the liquid, 

 and, as it is not altered by iodine solution, is called achroocellu- 

 lose. On hydrolysis it furnishes a mixtuie, chiefly of glucose 

 with compai-atively little mannose, and on this account is pro- 

 bably not a uniform substance. 



From the above reports one thing seems clear : that the 

 membrane of the yeast cell is a complex structure, both fi'om 

 the anatomical and the chemical point of view. This fact will be^ 

 regarded as so much the more certain when it is stated that no 

 one has yet succeeded in obtaining the so-called yeast cellulose 

 free from ash constituents and nitrogen. Schlossberger found 

 i.o per cent, of ash, and the preparations made by Salkowski 

 contained between 1.7 and 2.6 per cent., whilst Liebermann 

 and BiTTO (I.) found 1.8 per cent, in theirs. It does not do, 

 however, to launch out into theories respecting the significance 

 of these inoi'ganic constituents, the more so because the com- 



