MUC'()1{ KKKMKXTATIUXS. 83 



in this respect ut teiiipeiaUuiv, below 15° C. The weakest of all 

 Beeuisto be /{/ii::<>j,Uf: ///<//vVa//*, which.uLronlin^'to Bkekklu ( XV.), 

 cejises its activity as soon as 1.5 per cent, of alcohol luis Ijeen 

 forineil. X^one of these species uf Mucor ran be use<l fur distil- 

 lery purposes, since they are far surpassed in competition by a 

 number of true yea.sts, which are capable of pro<lucing an equal 

 (juantity of alcohol in a much shorter time, and also to cau-rv on 

 the fermentation much fiu-ther. With respect to a few other 

 species, proposed and euiploycd for this purpose, further particu- 

 lars will be found in §5 240 and 242. 



Carbon dioxide, being the most importmt, in quantity, of the 

 otiii-r pioducts ol' intramolecular respiration in Mwurt-'i^, will l)e 

 dealt with next. The reliable quantitjitive deternunations of 

 the production of this gas are very few in number, and for these 

 we are mainly iiidel)ted to Firz (IX.) and (Jayox (VI.). The 

 former worker, as the mean of nine experiments with Mwor 

 raremomiii, determined the ratio (by weight) of alcohol to carbon 

 <lioxide as 100: 123.1 ; an<l Gayon obtained similar values for 

 Mw'or i-ii-i-iii'lhiihs^ whereas, according to the (Jay-LusNic 

 eipiation, the ratio should be 100 : 95.6. The formation of alde- 

 hyde and succinic acid in this process was first observed in 

 cultures of Mwor nC'rinottti.'i by Fitz, and in those of .1/. ••irriwU- 

 oiilfK by Gayou, the last-named estimating the amount of this 

 acid as 2.07 grms., an<l the amount of the resulting glycerin 

 as 0.92 grm., per 100 grms. of saccluu-ose consumed. These 

 experiments with Mw<,r nv'-iiinsus were afterwards resumed, with 

 cultures of leliable purity, by O. Emmekli.nl; (111.), who obtiined 

 the following results from a culture grown for three weeks in a 

 nutrient solution of s;iccharose 4ml minenil .><;ilts, at 25° C, air 

 Ijeing excluded: alcohol, 1.46 percent.; succinic acid, 0*02 per 

 cent. ; glycerin, 0.12 per cent. The mutual iiitio between these 

 three products is 100 : i .4 : S.3. The amount of succinic acid seems 

 to differ with different species; at least HitKKELD (XIII.) .states, 

 on the basis of his experiments with Jilii.:ii/ius 7//«/r//-a«,<, Mu-nr 

 iiucedo, and M. raceinom^, that cultures of the first of these 

 organisms yield the relatively largest pro{>ortion of acid, and 

 tho.se of the third tiie sm.illest, though still more than is furnished 

 l)y beer yeast under similar conditions. The.so results pre- 

 sumably relate solely to succinic acid ; at lea.st this is probably 

 the case with .1/. ruri'iiiosit.t, since, according to Vu. HioiutiE (I.), 

 this organism does not prcxluce any volatile acids. Pix>duct.s of 

 the ester cla.ss have been often ob.servod to result from the 

 intramolecular respinition of Mueontv ; e.g. an otlour i-esem- 

 Iding that of pears, in cultures of .)f. ru'emosiw by Brefeld. 

 and one recallim: that of plums, in .l/'/-./- ./r.-//;' //..//.> bv 

 Gayon. 



We will now in.juire as to the kinds of carbohydrates which 

 may be ilrawn upon by the Mm-oon for the purjK..-o of forming 



