268 THE BLOOD. 



the blood, or on dissolving the blood-corpuscles of one kind of animal 

 in the serum of another (LANDOIS, stroma-fibrin) ; i.e., in the so-called 

 hcrmagglutination, a clumping of the red blood-corpuscles into clusters 

 takes place. This agglutination can be brought about by bodies 

 similar to the ha3molysines and also by serum constituents pro- 

 duced normally or by immunization. It has not been shown that 

 a fibrin formation from the stroma takes place. Fibrinogen has only 

 been detected in the red corpuscles of frog's blood (ALEX. SCHMIDT and 



SEMMER 1 ). 



Closely related to the anatomical and chemical structure of the erythro- 

 cytes is the question which is important, for the metabolism in the blood, 

 as to the permeability of the erythrocytes, that is, their power of taking 

 up substances of different kinds. This question as well as the permeability 

 of the blood-corpuscles for anions under the influence of carbon dioxide 

 has been discussed in a previous chapter (II, page 33) . 



The mineral bodies of the red corpuscles will be treated in connection 

 with their quantitative constitution. 



The constituent of the blood-corpuscles existing in greatest quantity 

 is the red pigment haemoglobin. 



Blood-pigments. 



According to HOPPE-SEYLER the coloring-matter of the red blood- 

 corpuscles is not in a free state, but combined with some other substance. 

 The crystalline coloring-matter, the hemoglobin or oxyhsemoglobin,. 

 which may be isolated from the blood, is considered, according to HOPPE- 

 SEYLER, as a cleavage product of this compound, and it acts in many 

 ways unlike the questionable compound itself. This compound is insoluble 

 in water and uncrystallizable. It strongly decomposes hydrogen peroxide 

 without being oxidized itself; it shows a greater resistance to certain 

 chemical reagents (as potassium ferricyanide) than the free coloring- 

 matter; and, lastly, it gives off its loosely combined oxygen much more 

 easily in vacuum than the free pigment. To distinguish between the 

 cleavage products, the haemoglobin and the oxyhaemoglobin, HOPPE- 

 SEYLER calls the compound of the blood-coloring matter of the venous 

 blood-corpuscles phlebin, and that of the arterial arterin. Other investiga- 

 tors, such as H. IT. KOBERT and BoHR, 2 the latter calling the pigment 



1 Landois, Centralbl. f. d. med. Wissensch., 1874, 421; Schmidt, Pfluger's Arch., 

 11, 550-559. 



2 Hoppe-Seyler, Zeitschr. f. physiol. Chem., 13, 479; H. U. Robert, Das Wirbeltier- 

 blut in mikro-kristallogr. Hinsicht, Stuttgart, 1901; Bohr, Cenrtalbl. f. Physiol., 17, 

 p. 688. 



