650 diabhtes 



chronic pentosuria 24 

 Tilt' literatuiv coutaiiis repoi'ts of some 30 cases in which consid- 

 erable (jnantities of pentose have Won excreted steadil}^ in the urine 

 regardless of the character or (inantity of the food. Even during a 

 fast the quantity excreted has remained virtually constant in some 

 cases. Outputs as high as 36 grams per day have been recorded. 

 Such quantities of pentose could not be introduced into the body from 

 without by any known means without causing pentosuria of marked 

 degree. Accordingly, in some cases there is either an overproduction 

 of endogenous pentose, or an abnormal entry into the blood stream 

 of pentose which is normally bound in the tissues. The process would 

 then be analogous to that in which lactose from the mammary glands 

 occasionally gains access to the general circulation and appears in the 

 urine. This conclusion is confirmed by the work of Bial, Blumenthal 

 and Tintemann, who found that certain pentosurics displayed no les- 

 sened tolerance for administered pentose. The origin of the pentose 

 is unknown. Nucleo-protein of cell nuclei, and galactose have been 

 suggested as possible sources. The disease has been found in differ- 

 ent members of the same family and appears to be a harmless anomaly. 

 The pentose found in the urine in cases of all types has sometimes 

 been reported as optically inactive, sometimes as dextro- or levo- 

 rotatory: 1-arabinose (dextro-rotatory), d-xylose and d-xyloketose 

 appear to have been identified.-"' 



HEXOSES 



Chemical Introduction. — Structural theory demands the existence of 32 

 isoiiicric liexose su<>ars of the formula CoH,„0„. The behavior of the hexoses 

 when dissolved in very dilute alkali makes it convenient to consider tliem in four 

 natural series of oifrht members each. Thus one series comprises tlic S hexoses 

 whose structural formuUie ai)pear below. This may be called tlie d-filucose series. 



(1) (2) (3) (4) (5) (6) (7) (8) 



CHO CHO CHiOH CHO CHO CH.OH CH^OH CHoOH 



H-i-OH HO-C-H CO H-C-OH HO-C-H CO H-COH HO-C-H 



I I I I I I I I 



HO-C-H HO-C-H HO-C-H H-C-OH H-C-OH H-C-OH CO CO 



I I I I I I ! I 

 H-6-0H H-C-OH H-C-OH H-C-OH H-C-OH H-C-OH H-C-OH H-C-OH 



II I I I I I I 

 n-(^'-OH H-r-OH H-COH H-C-OH H-C-OH H-C-OH H-C-OH H-C-OH 



r r 1 I I I I 



CH,OH Cn.OH CH.OH CH,OH Cn,OH CH.OH CH.OH CHsOH 



d-i)seudo 

 dglucase d-mannose d-fructose d-allose d-latose fructose ad-ghitose /3-d ghitose 



Tliere is also an l-<:lucose series in which the members are the mirror imajres 

 of the above. There is a tliird series coniprisin<r d-galactose, d-talose, d-tajiatose, 

 l-sorl)ose, 1-idose, l-<;ulose and alplia and beta d-galtose; and a fourtii series whose 

 relatioiisliip to the d-<ralaclose series is tlie same as that of the l-jrhicose to the 

 d-glucose series. Consideration of tlie d-<ilucose series will liriiijj: out tlie priii- 



•.;4 See fiarrod. "Inliorn I'Jrors of Mctaliolism." (~)xfor(l :Mcd. Pulil., I'.IO'.l; l.iuicct. 

 .lulv, 1 !)()!». 



■^■^Vor literature see lliller, Jour. Biol. C'liem., VMl (30), 120. 



