560 LECTURE XXIV. 



ber that the red blood-corpuscles of birds contain nuclei and considerable 

 amounts of nuclein substances. It is perfectly possible that the presence of 

 such an impurity accounts for the apparent phosphorus content in the hemo- 

 globin of different species of birds, whose blood has been studied. This 

 assumption appears more probable when we state that the oxyhemoglobin 

 from birds has never been prepared in a satisfactory manner, nor purified 

 to the extent accomplished with that from animals, and, moreover, if we 

 examine the beautifully formed crystals under the microscope, we shall 

 find that they may include within themselves considerable amounts of 

 impurity. In the hemoglobin from horses, pigs, and cattle, two atoms of 

 sulphur are present for each atom of iron, while in the blood of dogs, the 

 iron is to the sulphur as 1:3. We may also mention the fact that the 

 various oxyhemoglobins contain different amounts of water of crystalliza- 

 tion. It is still an open question whether the oxyhemoglobin from one and 

 the same species of animals is always identical. C. Bohr 1 holds that this 

 is not the case. He believes he has proved that differences exist by deter- 

 mining the power of combining with oxygen in different fractions of crystals 

 from a single kind of blood. Hlifner, 2 whose investigations in this field 

 have been thorough and most carefully made, holds that such an assumption 

 is not justifiable. It must be admitted that it is not easy to prove beyond 

 all doubt that there is an actual difference in different oxyhemoglobins. 

 There is always the possibility that the observed differences may arise from 

 secondary changes which have taken place in the oxyhemoglobin that is 

 under examination. 



As regards the combination of the oxygen in hemoglobin, we have 

 already seen that only the hemochromogen takes part in this, and that the 

 iron is of much significance here. 



The spectroscopic behavior of oxyhemoglobin is very characteristic. A 

 dilute solution shows in the spectroscope two absorption bands in the yellow 

 and green, between the Fraunhofer lines D and E. The band near the D 

 line is narrower than that near the E line. Arterial blood gives the same 

 absorption spectrum on account of the presence of oxyhemoglobin in it. 

 We must also add that reduced oxyhemoglobin, the true hemoglobin, like- 

 wise shows characteristic absorption bands. A solution of hemoglobin, 

 of not too great a concentration, shows a single broad band, not very 

 sharply defined, lying between the D and E lines; in fact, this band extends 

 a little beyond the D line into the red end of the spectrum. Venous blood 

 shows such a spectrum, although, except in cases of suffocation, there is 

 always some oxyhemoglobin present. The greater part of the oxyhemo- 

 globin in such blood has, however, been reduced. Consequently venous 

 blood does not have the bright red color of arterial blood. It is darker 



1 Zentr. Physiol. 4, 249 (1890). 

 3 Arch. Anat. Physiol. 1894, 130. 



