ALia'.MlNolU MrciXorS SUBSTANX'ES. ,8r 



one may conclud*' that it is e hi borate" I by the yeast cells them- 

 selves. Of course lh« further question must be left undecided 

 whether, in nutrient solutions that already contain albumin, 

 the amount is increased by some jtortions of this latter sub- 

 stance. 



Heer yeast (sedimental yeast) when well shaken up with 

 ether (i:i), tjikes up a cei-tain quantity of tlie sjime, the amount 

 depending on the percent;i>;e of this albuniiik and the aforesaid 

 mucinous substances present. Yeast from the upper hiyer 

 takes up two to three parts by volume of ether, but core yeast 

 only about one part, the mucinous substances forming bubbles 

 charged with ether. In tlicsi- laboratory experiments the ether 

 plays the sjime part as caibon dioxide iloes in practical fermen- 

 tation in the vat ; and as the mucinous substances do not 

 remain in the .se<limental yeast, but are in part ceded to the 

 supernatjint liquid, they are able, in the above-described manner, 

 to effect a lirmer retention of the carbon dioxitle than can be 

 done by mere physical .solution. Oon.sequently, under certain 

 circumstances, tln-y may considerably augment the socalled 

 permanent absorptive capacity for carbon dioxide on the part of 

 the beer. 



The fact that a soluble albuminoid takes part in the forma- 

 tion of the " head " or scum thrown up by fermenting wort 

 was first suspected l>y Hubich, and then proved, by isolation, by 

 C. LiXT.VEU, sen., and Kkischaueu in 1S76. This froth glutin 

 (Krauesengliitin) is .sjiid to originate in the wort or the malt. 

 liy means of comparative fermentixtion experiment's with «lif- 

 ferent beer yeasts, it was then est;ibli.shed by Alb. Reicii.^kd 

 (III.) that, in adtlition to this malt albuminoid, the presence of 

 certain mucinous excretiims (especially those of an albuminoid 

 character) from the yeast is essential to the formation of a 

 normal " head " composed of tine bubbles. The condition of these 

 formative materials in the head at different stiiges of fermenta- 

 tion has not vet been more doselv investigated. 



In the case of a liquid ab.solutely tlevoid of vi.scosity and 

 free from mucinous constituents, the bubbles of carl>on dioxide 

 libei-ite<l in the interior would immediately unite to large ones 

 and make their escape without delay as .soon as they arrivetl 

 at the sinface. Hy means of these mucinous substances, 

 however, each bubble of gas is surrounded by a tough envelope 

 at the instant of liberation, and thereby preventetl from be- 

 coming merged into others. The.se bubbles collect on the 

 surface of the liquid, stick together, and thus form by degrees 

 the line, permanent "head" so «lesired by the brewer and the 

 pressed-yeast maker. Tiie asi'ending bubbles al.so carry to the 

 surface other constituents of the fermenting wort, and incor- 

 porate them with the structure of the head, chief among these 

 being yeast cells (see below), then fragments of tissue from the 



