CHEMICAL BASIS OF THE ANIMAL BODY. Ill 



the small intestine where the active agent is without doubt an 

 enzyme 1 . From this it appears that cane-sugar conforms to the 

 apparently general rule that the carbohydrates leave the alimentary 

 canal as dextrose. 



Cane-sugar readily undergoes a lactic-acid fermentation in presence 

 of sour milk to which zinc oxide is added for the fixation of the acid as 

 it is formed. 



2. Maltose. C 12 H 22 O n + H 2 0. 



This is the sugar which is characteristically formed, together with 

 dextrins, by the action of malt-extract (diastase) on starch-paste. It 

 was first described by Dubrunfaut 2 as arising in this way, but its 

 existence was for some time doubted until firmly established by 

 O'Sullivan 3 . Later researches showed that it is similarly the chief 

 sugar which is formed by the action of saliva and pancreatic juice 

 upon starch-paste or upon glycogen, being accompanied in the case of 

 pancreatic juice by a variable but distinct amount of dextrose if the 

 action of this secretion be prolonged 4 . Maltose is also formed by the 

 action of dilute acids upon starch-paste, but in this case it is difficult 

 to prevent the simultaneous formation of dextrose into which it is 

 readily converted by acids, yielding 98 99 p.c. of the latter sugar 5 . 

 It is therefore usually prepared from the products of the action of 

 malt-extract on starch- paste 6 . 



Maltose is very soluble in water, also in alcohol, but less so in the 

 latter solvent than is dextrose. It crystallises in fine needles which 

 are however not very easily obtained. Solutions of maltose are 

 dextro-rotatory and reduce metallic salts ; it is therefore not easily 

 distinguished from dextrose by merely qualitative tests. As the 

 necessity of discriminating between the two sugars is one of frequent 

 occurrence, the following characteristic differences between their 

 optical and reducing powers are of great importance. For maltose in 

 10 p.c. solution at 20C. (a) D = + 140 7 , for dextrose (a) D = + 52-5. When 



1 Leube, Centralb. f. d. med. Wiss. 1868, S. 289. Paschutin, Arch. f. Anat. u. 

 Physiol. Jahrg. 1871, S. 374. Bernard, Gaz. med. de Paris, 1873, p. 200. Brown 

 and Heron, Liebig's Ann. Bd. cciv. (1880), S. 228. Proc. Roy. Soc. No. 204, 1880, 

 p. 393. Vella, Moleschott's Untersuch. Bd. xin. (1881), S. 40. 



2 Ann. Chim. et Phys. (3) T. xxi. (1847), p. 178. 



3 Jl. Chern. Soc. Ser. 2, Vol. x. (1872), p. 579. Cf. Musculus u. Gruber, Zt. 

 physiol. Chem. Bd. u. (1878-79), S. 177. 



4 Musculus u. von Mering, Zt. f. physiol. Chem. Bd. i. (1877-78), S. 395; u. 

 (1878), S. 403. Kiilz, Pfliiger's Arch. Bd. xxiv. (1881), S. 81. Brown and Heron, 

 Liebig's Ann. Bd. cxcix. (1879), S. 165; Bd. cciv. S. 228. Proc. Eoy. Soc. No. 204, 

 1880, p. 393. von Mering, Zt. f. physiol. Chem. Bd. v. (1881), S. 185. 



5 Meissl, Jn.f. pr. Chem. (2), Bd. xxv. (1882), S. 114. 



6 Soxhlet, Jn. f. pr. Chem. (2), Bd. xxi. (1880). Herzfeld, Liebig's Ann. Bd. ccxx. 

 (1884), S. 211. 



7 Meissl, loc. cit. Brown and Heron make it less= +135-4. 



