350 VEHICLES OF CHEMICAL CORRELATION 



from the liver possess marked ability to inhibit coagulation, the origin 

 of the inhibition being the delaying or prevention of the formation of 

 thrombin from prothrombin by calcium salts. 



THE CHEMISTRY OF HEMOGLOBIN. 



The red coloring-matter in the erythrocytes of the vertebrates is 

 hemoglobin, a compound protein which is split by hydroylsis into 

 a histone-like protein, Globin, and an iron-containing organic acid, 

 Hematin. By reason of the power which it possesses of forming a readily 

 dissociable compound with Oxygen, hemoglobin accomplishes the trans- 

 portation of oxygen from the lungs to all the tissues of the body. 

 Other pigments fulfilling a like function are found widely dispersed 

 among invertebrate animals. Thus in the Arachnids Crustacea and 

 Mollusca there is found a protein containing copper, which has been 

 termed hemocyanin and which becomes blue when saturated with 

 oxygen, and colorless when the oxygen is liberated again. 



The content of Iron in hemoglobin is identical in all species of animals. 

 The following figures, for example, are given by Jaquet: 



Hemoglobin from 



the blood of: Per cent, of iron. 



Dog 0.0336 



Horse . . . . i . . . - . . . ". ...... 0.0335 



Ox ;-..... ... 0.0336 



Hen . . . : . .;:.. . . . 0.0335 



Assuming that each molecule of hemoglobin contains one atom of 

 iron, this implies a molecular weight for hemoglobin of 16,669 while 

 complete analyses indicate an empirical formula approximating to the 

 following: 



C759Hl20 8 N 2 loS2FeO204 



If we examine the Absorption-spectrum of well aerated or arterial blood 

 or of a pure solution of hemoglobin which has been shaken with air 

 or oxygen, we find that the transmitted light contains two well-marked 

 absorption-bands, lying between the Fraunhofer lines D and E. The 

 band nearest to D, termed the a band is narrower, but darker and 

 sharper than the ft band lying nearer to E. On dilution, the & band 

 is the first to disappear. On concentration the bands become broader 

 and finally appear to coalesce. The center of the a band corresponds 

 to the wave-length X = 579, that of the ft band to the wave-length 

 X = 542. In the Photographic Spectrum a band may also be seen in the 

 ultraviolet region, near to G, having its center at the wave-length 

 X = 415. This band, which was first detected by Soret, has been 

 proposed as a means of detecting hemoglobin in high dilutions, since 

 it is still perceptible in solutions containing only one part of hemoglobin 

 in 40,000, while the bands in the visible spectrum are no longer per- 

 ceptible at a dilution of one in fifteen thousand. The absorption-band 



