260 THE BLOOD. 



of the so-called rest nitrogen, i.e., that nitrogen which remains in the serum 

 after the complete removal of the coagulable proteins. As representatives 

 of the bodies occurring as rest nitrogen in the serum we must in the 

 first place mention urea, also creatine, carbamic acid, ammonia, hippuric 

 acid, phosphocarnic acid (PANELLA 1 ), traces of indol (HERViEUX 2 ), 

 perhaps also uric acid found by ABELES 3 in human blood, while LETS CHE 

 could not find any in horse-blood. LETSCHE could not find any mon- 

 amino- or diamino -acids and purine bases which, like lysine (NEUBERG 

 and RiCHTER 4 ), leucine, tyrosine and bile-acids are found in blood serum 

 under pathological conditions. 



According to BROWINSKI 5 proteic acids (see Chapter XV) occur in 

 the serum. As above stated, the occurrence of proteoses is disputed. 

 We have several investigations on the occurrence of amino-acids (v. 

 BERGMANN, HOWELL, LETSCHE and others ) which make the occurrence 

 of these very probable, and recently BiNGEL 7 has been able to show the 

 presence of glycocoll in normal ox-blood. That the quantity of rest 

 nitrogen is larger during digestion than in starvation requires further 

 confirmation (V. BERGMANN and LANGSTEIN, HOHLWEG and H. MEYER 8 ). 



The pigments of the blood-serum are very little known. Besides 

 other pigments horse-serum contains, as first shown by HAMMARSTEN, 

 bilirubin, which according to RANC is the only pigment of the serum of this 

 animal. This pigment occurs according to BIFFI and GALLI in especially 

 large quantities in the blood of new-born. 9 The yellow coloring-matter 

 of the serum seems to belong to the group of luteins, which are often 

 called lipochromes or fat-coloring matters. From ox-serum KRUKEN- 

 BERG 10 was able to isolate with amyl alcohol a so-called lipochrome whose 

 solution shows two absorption-bands, of which one encloses the line 

 F and the other lies between F and G. 



The mineral bodies in serum and plasma are qualitatively, but not 

 quantitatively, the same. A part of the calcium, magnesium, and phos- 

 phoric acid is removed on the coagulation of the fibrin. By means of 



1 Panella, cited in Virchow's Jahresb., 1902, 150. 



2 Compt. rend. soc. biol., 56. 

 8 Wien. raed. Jahrb., 1887. 

 4 Deutsch. med. Wochenschr., 1904. 



6 Zeitschr. f. physiol. Chem., 54 and 58. 



8 v. Bergmann, Hofmeister's Beitrage, 6; Howell, Amer. Journ. of Physiol., 17; 

 Letsche, 1. c. 



7 Zeitschr. f. physiol. Chem., 57. 



8 v. Bergmann and Langstein, Hofmeister's Beitrage, 6; Hohlweg and Meyer, ibid., 

 11. 



9 Hammarsten, see Maly's Jahresb., 8 (1878); Ranc, Compt. rend. soc. biol., 62; 

 Biffi and Galli, Journ. de Physiol. et Path., 9 (1907). 



10 Sitz. Ber. d. Jen. Gesellsch. f. Med., 1885. 



