BLOOD SERUM. 257 



serum. According to the investigations of many workers 1 the sugar 

 found is dextrose. STRAUSS 2 has also detected levulose in blood-serum 

 and in transudates and exudates. The question as to the occurrence of 

 other varieties of sugar, such as isomaltose (PAVY and SIAU) and pentose 

 (LEPINE and BOULUD S ), in blood serum is still undecided. ASHER and 

 ROSENFELD and MICHAELIS* and RONA in a more conclusive manner, 

 have shown that at least a considerable part of the sugar can be removed 

 from the blood by dialysis, hence it must exist in solution in the free 

 state. These observations do not exclude the possibility of the existence 

 of another part of the sugar which is in combination with protein. 

 LEPINE and BOULUD 4 could only obtain a diffusion of the sugar by a 

 short dialysis from serum 12 hours old, but not from perfectly 

 fresh serum, an observation which somewhat diminishes the conclusive- 

 ness of MICHAELIS and RONA'S experiment with 24-hour dialysis. A 

 further testing of this question is therefore very desirable. Besides 

 sugar, the blood-serum contains, as first shown by J. OTTO, another 

 reducing non-fermentable substance whose quantity in rabbits' blood 

 is about one-quarter of the total quantity of reducing substance (N. 

 ANDERSSON). The statements of JACOBSEN, HENRIQUES, and BiNG, 5 

 that this substance is jecorin or lecithin sugar, do not have sufficient 

 foundation, and the identity with jecorin becomes more striking as the 

 existence of a jecorin is on the whole doubtful. The nature of another 

 carbohydrate in the blood, which is neither dextrorotatory nor reducing, 

 and which has been called virtual sugar by its discoverers, LEPINE and 

 BOULUD, 6 is also undetermined. The virtual sugar is more abundant in 

 the blood of the right ventricle than in the arterial blood, and this in 

 turn is richer than venous blood. In the passage of the blood through 

 the lungs the virtual sugar is converted into ordinary sugar; this may 

 also occur in the capillaries of the greater circulatory system. 



Conjugated glucuronic acids, which probably originate from the 

 form-elements, have been shown to occur in blood by the researches of 



1 See v. Mering, Arch. f. (Anat. u.) Physiol., 1877 (this article contains numerous 

 references); Seegen, Pfluger's Arch., 40; Miura, Zeitschr. f. Biologie, 32. 



2 Fortschritte d. Mediz., 1902. 



3 Pavy and Siau, Journ. of Physiol., 26; Lupine and Boulud, Compt. rend., 133, 135, 

 and 136. 



4 Rosenfeld, Centralbl. f. Physiol., 19, p. 449; Lepine and Boulud, Compt. rend., 

 143; Asher, Biochem. Zeitschr., 3; Michaelis and Rona, ibid., 14. 



5 Otto, Pfliiger's Arch., 35 (a good review of the older literature on sugar in the 

 blood); N. Andersson, Biochem. Zeitschr., 12; Jacobsen, Centralbl. f. Physiol., 6, 368; 

 Henriques, Zeitschr. f. physiol. Chem., 23; Bing, Skand. Arch. f. Physiol., 9; see also 

 P. Mayer, Biochem. Zeitschr., 1 and 4 on jecorin and blood sugar. 



6 Compt. rend., 137, 144, 147. 



