CHEMICAL BASIS OF THK ANIMAL T.oDV. 105 



above method it is possible to obtain the crystals from fluids 

 which contain only 0-5 gnu. per litre. 



An important property of dextrose is its power of undergoing 

 fermentations Of these the principal are : (1) Alcolwlic. This is 

 produced in aqueous solutions of dextrose, under the influence of 

 yeast. The decomposition is the following : CH 12 O C = 2CH 6 O -f- 

 2CO 2 , yielding (ethyl) alcohol and carbonic anhydride. Higher 

 alcohols of the fatty series are found in traces, as also are gly- 

 cerin, sui -cinic acid, and probably many other bodies. The fer- 

 mentation is most active at about 25C. Below 5C. or above 

 45C. it almost entirely ceases. If the saccharine solution con- 

 tains more than 15 per cent, of sugar it will not all be decom- 

 posed, as excess of alcohol stops the reaction. (2) Lactic. This 

 is best known as occurring in milk when it turns sour owing to 

 the conversion of lactose into lactic acid. But dextrose and 

 other sugars may also be converted into lactic acid (C 6 H 12 O = 

 2C S HO 8 ), the conversion being ordinarily due to the presence 

 of some specific micro-organism l which is specially active in 

 presence of decomposing nitrogenous material, such as decaying 

 cheese. 3 A similar change is rapidly produced when dextrose is 

 mixed with iinely divided gastric mucous membrane. 3 There is 

 also some evidence of the existence of an unorganised ferment 

 (enzyme) in the mucous membrane of the stomach which can 

 convert lactose and dextrose (?) into lactic ficid. 4 On prolonged 

 standing the lactic fermentation is apt to pass into (3) Butyric. 

 This results from the appearance and action of another specific 

 organised ferment on the first formed lactic acid, the change 

 IM -in g accompanied by the evolution of hydrogen and carbonic 

 anhydride 



2C 3 H 6 0, = C,H 7 . COOH. + 2CO S + 2H 2 . 



Lactic and butyric fermentations are most active at 35 and 40 J 

 lively; they probably occur constantly in the alimentary 

 eanal with a carbohydrate diet and may in some cases lie remark- 

 ably predominant The hydrogen evolved during butyric fermen- 

 tation probably plays some important part in the production of 

 the fii-cal and urinary pigments from those of bile (see below). 



I>e\tr..-e i- tin- sujjur which is characteri>t irally formed by the 

 action i if boiling dilute mineral acids <m SIIUMI- i-f the c.nie-^ugar 

 group, iinil (in March and dextrin. When it is dissolved in concen- 

 trated sulphuric acid it i> >aid to be partly n-com erted into a. true 



1 F.isti-r. /'<nli. -SV. Trnns. 1^-7 :. ji fJ.Y <j,i.irt. Jl. Micros. Sri. Vol. xvni. (1878), 



&177. Miirpm.-uui. (.'rntr<ill> .nillinisfitl Brffftnsonglhft. II. (1886), 8. 117. 



;,.t. |8M A I. st. iii M:ily'> r,.r,.-ht. Iss], S. 468. 



- Ili-liscli, I'rr/xinilliin i>f' tin-fir iicul. Lictii^'s Ati. IM I \I. (l-7), S. 174. 



. i.i.-i.i- 1 ^ .JH,, i;,i ouaaa (1874), 8. M7. 

 4 BbUBBMnton is\\.-.li|i). See Almt. in Maly's lirr IM n. (1872), S. 118. 



