BLOOD SERUM. 265 



Fat occurs from 1-7 p. m. in fasting animals. After partaking of 

 food the amount is increased to a great extent. Fatty acids, or soaps, 

 glycerin (NiCLOUx, FR. TANGL, and ST. WEISER l ) phosphatides and 

 cholesterin are also found. Cholesterin occurs, according to HURTHLE 2 , 

 at least in part, as fatty-acid esters (serolin according to BOUDET) . Accord- 

 ing to LETSCHE 3 free cholesterin probably also occurs in the serum. 



Sugar seems to be a physiological constituent of the plasma and 

 serum. According to the investigations of many workers 4 the sugar 

 found is glucose. STRAUSS 5 has also detected fructose 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 pen- 

 tose (LEPINE and BOULUD 6 ) , in blood serum is still undecided. ASHER 

 and ROSENFELD and MICHAELIS and RON A 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 7 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 conclusiveness 

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

 ther testing of this question is therefore very desirable. 



The quantity of sugar in the serum or plasma is for man 0.6-1 p. m. 

 calculating the total reduction as glucose, and in animals about the same 

 but in rabbits considerably higher or 2.2 p. m. 8 Besides the sugar, the 

 blood contains, as first shown by J. OTTO, also another or perhaps several 

 reducing substances, a part existing in the serum and another part in the 

 blood-corpuscles. We will discuss the nature of these bodies as well 

 as the so-called virtual sugar and glycolysis in speaking of the division 

 of the sugar in the blood-corpuscles and plasma in connection with 



1 Nicloux, Compt. Rend. soc. biol., 55; Tangl and St. Weiser, Pfliiger's Arch., 115. 



2 Hiirthle, Zeitschr. f. physiol. Chem., 21, where Boudet is also cited. In regard 

 to the quantity of these esters in bird-serum, see Brown, Amer. Journ. of Physiol., 2. 



3 Zeitschr. f. physiol. Chem., 53. 



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

 references); Seegen, Pfliiger's Arch., 40; Miura, Zeitschr. f. Biologic, 32. 



6 Fortschritte d. Mediz., 1902. 



6 Pavy and Siau, Journ. of Physiol., 26; Lepine and Boulud, Compt. Rend., 133, 

 135, and 136. 



7 Rosenfeld, Centralbl. f. Physiol., 19, p. 449; Le"pine and Boulud, Compt. Rend., 

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



8 See E. Frank, Zeitschr. f. physiol. Chem., 70; Lyttkens and Sandgren, Bioch. 

 Zeitschr., 21 and 26. 



