94 PHYSIOLOGICAL CHEMISTRY. 



of the body, by its capacity for absorbing oxygen, which it retains in 

 the form of a loose combination. According to the average result of 

 various experiments one gramme of hemoglobine, in watery solution, 

 will absorb 1.2T cubic centimetres of oxygen. It is again deprived of 

 its superabundant oxygen under the influence of diminished pressure, 

 heat, or the continued displacing action of hydrogen or nitrogen. Its 

 hue varies according to these two conditions, being bright red in the 

 former case, dark red or purple in the latter. It is therefore known 

 under two different forms; namely, that of " oxyhemoglobine," con- 

 taining its full quota of loosely combined oxygen, and that of " reduced 

 hemoglobine," in which the surplus oxygen has been removed. Its 

 presence, in either one or the other of these conditions, is the cause of 

 the color of arterial and venous blood. 



Spectrum of Hemoglobine. All transparent coloring matters, when 

 viewed by transmitted light, absorb or arrest certain portions of the 

 luminous ray and allow others to pass. The transmitted beam, there- 

 fore, appears colored, because only a part of the original white light 

 reaches the eye. If, after passing through p, colored solution, the 

 luminous ray be analyzed into its spectrum by means of a prism, as in 

 the spectroscope, it can then be seen exactly wbat colors have been 

 allowed to pass the solution, and what have been retained by absorption. 

 Wherever a color has been absorbed or arrested, its place in the spec- 

 trum is occupied by a dark band. Such a band occurring in the 

 spectrum of any colored substance, is called an " absorption band," and 

 becomes a distinguishing feature in the spectrum of that substance. 



The spectrum of hemoglobine, in an aerated solution, is distinguished 

 by two separate absorption bands. The first is a comparatively nar- 

 row, dark, and well-defined band situated in the yellow, a little to the 

 right of the line D. The second is a wider, fainter, and more diffused 

 band, at the commencement of the green, and a short distance to the 

 left of the line E. Both bands are, therefore, contained in the space 

 between the lines D and E. Beyond E the green and blue of the spec- 

 trum are visible, but the light diminishes gradually and disappears near 

 the end of the blue, so that the indigo and violet parts are completely 

 dark. Fresh blood, diluted with water, will give the same appearance. 



If the solution be concentrated, or viewed in a very thick layer, it 

 is too opaque for spectroscopic examination, and may shut off all the 

 light of the spectrum except a little of the red and orange; if too 

 dilute, it will fail to exhibit its distinguishing characters. A solu- 

 tion of a certain strength, which allows abundance of light to pass, 

 and is yet sufficient to cause its absorption at particular points, is 

 best suited for examination. With pure hemoglobine, according to 

 Preyer, a solution of about 1.5 parts per thousand gives the most 

 marked results. With fresh blood, if one volume of the defibrinated 

 blood be diluted with one hundred volumes of water, and the mixture 

 viewed in a layer of one centimetre, all the characteristic traits of the 

 spectrum will be distinctly shown. (Fig. 13, I.) 



