THE CARBOHYDRATES. 3 
physiological interest, ami their chemical relationships and reactions 
will be found described in works on chemistry. 1 
Those which are of physiological importance are the hexoses and 
their derivatives. Nearly aU the carbohydrates with which we have 
to deal in the animal body contain either six carbon atoms, or some 
multiple of six. The same is true of those which are used as food. The 
remainder are either synthetical products of the chemical laboratory, or 
mure or less rare products "i the vegetable world. 
But to this rule there is one exception : the pentoses do possess some 
physiological importance. When Hammarsten - was investigating the nucleo- 
proteid material he separate 1 from the pancreas, he found that by boiling it 
with dilute mineral acid he obtained a reducing substance. This formation 
of a reducing sugar-like substance from nuclein is not unique, as Kossel 3 and 
his pupils have obtained a similar product from yeast-nuclein. The sugar, 
however, does not ferment with yeast, but, like the pentoses, gives a red 
coloration with phloroglucinol and hydrochloric acid, and by distillation with 
hydrochloric acid yields furfuraldehyde. An osazone is obtainable from it 
in the form of fine rosettes of crystals, melting at 158' to 160° C, and these 
appear to be identical with those prepared from pentoses by E. Salkowski 
and M. Jastrowitz. 4 
The physiological action of pentoses was investigated by W. Ebstein. 5 
When xylose or arabinose, dissolved in Avater or coffee, are taken with the 
food, they rapidly appear in the urine; they are not assimilated. The use of 
fruits, such as pears, that contain pentosan's, the mother substances of pentoses, 
may lead to the appearance of the latter substances in the urine. It is 
of course important not to confound such a temporary condition with diabetes. 
Max Cremer' ; has investigated the physiological action of some of the rare 
sugars, especially their influence en the formation of glycogen. He found that 
in rabbits mannose increases the hepatic gtycogen, and that, though the 
pentoses readily pass into the urine, a small quantity is assimilated as glycogen. 
Lindeman and May T have confirmed Cremer's results. 
Salkowski 8 has investigated a large number of diabetic urines, but was 
unable to find pentose in any of them. Xevertheless, he found pentose in 
various other morbid conditions in the urine, in which their presence could 
not be attributed to diet. He suggests that in these cases they originate in 
the body from such nucleo-proteids as Hammarsten found in the pancreas, the 
processes of oxidation being lessened so that they were not broken up into 
simpler materials. 
We can now proceed to the study of the carbohydrates concerning 
which we have more accurate physiological knowledge ; and these may 
be classified into the following three groups : — 
1 See article <: Sugars," Watts's "Dictionary of Chemistry," London, 1894, vol. iv. 
- ZtscJir. f. physiol. Chem., Strassburg, B<1. xix. S. 19. 
3 Kossel and Xeumann, Ber. d. deutsch. chem. Gesellsch., Berlin, Bd. xxvii. S. 2215. 
4 Centralbl. f. d. med. Wissensch., Berlin, 1892, Xos. 19 and 32. Blumenthal {fieri, klin. 
Wchnschr., 1897, Bd. xxxiv. S. 245) has obtained pentoses from numerous other nucleo- 
proteids. 
5 Virchows Archiv, Bde. exxix. S. 401 ; exxxii. S. 368 ; exxxiv. S. 361. 
6 Ztschr.f. Biol., Miinchen, Bd. xxix. S. 484. 
7 Chem. Centr.-BL, Leipzig, 1896, Bd. i. S. 932. 
8 Bed. klin. Wchnschr., Bd. xxxii. S. 364. See also Kiilz and Vogel {Ztschr.f. Biol., 
Miinchen, 1895, Bd. xxxii. S. 185). These observers found pentoses in only four out of 
sixty-four cases of human diabetes. But they are generally found in the severe forms of 
diabetes produced in dogs by the extirpation of the pancreas or by administration of 
phloridzin. 
