PHYSIOLOGICAL CHEMISTRY. 



The most important constituent of the blood-corpuscles from a 

 physiological standpoint is the red coloring matter. 



Blood-coloring Matters. 



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 haemo- 

 globin or oxy haemoglobin, which may be isolated from the blood, is 

 considered, according to HOPPE-SEYLER, as a splitting product of 

 this combination, and it acts in many ways like the questionable 

 combination itself. This combination is insoluble in water and 

 uncrystallizable. It strongly decomposes hydrogen peroxide with- 

 out being oxidized itself; it shows a greater resistance to certain 

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

 ing matter, and lastly it gives off its loosely-combined oxygen much 

 more easily in vacuum than the free coloring matter. To dis- 

 tinguish between the splitting products, the haemoglobin and the 

 oxyhaemoglobin, we may call the combination of the blood -coloring 

 matter of the venous blood-corpuscles phlebin, and that of the arte- 

 rial arterin (HOPPE-SEYLER). Since the above-mentioned combi- 

 nation of the blood-coloring matters with other bodies, for example 

 (if they really do exist) with lecithin, have not been closely studied, 

 the following statements will only apply to the free coloring matter, 

 the haemoglobin." 



The color of the blood depends in part on hcemoglobin and in 

 part on a molecular combination of this with oxygen, the oxyJimmo- 

 globin. We find in blood after suffocation almost exclusively haemo- 

 globin, in arterial blood disproportionately large amounts of oxyhae- 

 moglobin, and in venous blood a mixture of both. Blood-coloring 

 matters are found also in striated as well as in certain smooth mus- 

 cles, and lastly in solution in different invertebrata. The quantity of 

 haemoglobin in human blood may indeed be somewhat variable under 

 different circumstances, but amounts averaging about 14$ or 8.5 

 grammes have been determined for each kilo of the weight of the 

 body. 



The haemoglobin belongs to the group of proteids, and yields as 

 splitting products, besides very small amounts of volatile fatty acids 



