346 THE BLOOD. 



dilute hydrochloric acid, and is insoluble in an excess of the reagent. 

 With concentrated nitric acid it is thrown down in the cold, but not 

 from its heated solutions. Under certain conditions it can be coagu- 

 lated on boiling, but, unlike the other coagulable albumins, its coagu- 

 late is readily soluble in acids. It contains 54.97 per cent, of carbon, 

 7.2 per cent, of hydrogen, 16.89 per cent, of nitrogen, and 0.42 per 

 cent, of sulphur. In its behavior toward polarized light globin 

 behaves like a true albumin i. e., it is laevorotatory. The amount 

 of globin which can be obtained from the haemoglobin molecule is 

 quite large, and according to Schultz amounts to 86.5 per cent., 

 while 4.2 per cent, only is represented by the pigment itself. 



Isolation. A solution of oxyhaemoglobin in water, prepared at 

 a temperature of 40 C., is treated with dilute hydrochloric acid 

 until the red color changes to brown. This mixture is extracted 

 with 80 per cent, alcohol (one-fifth volume) and ether (one-half 

 volume) until the ether takes up no more coloring-matter. The 

 resulting aqueous-alcoholic solution is precipitated with ammonia, 

 filtered, and the precipitate dissolved in very dilute acetic acid. On 

 filtering, the globin is again precipitated with ammonia and col- 

 lected on a silk filter. After washing with absolute alcohol, then 

 with water, again with alcohol, and finally with ether, the substance 

 is dried first in the air and then at a temperature of 100 C. The 

 resulting material constitutes pure globin, as a yellowish loose 

 powder, which is not especially hygroscopic. 



Haemochromogen. The isolation of haemochromogen is rather 

 difficult, owing to the avidity with which it combines with oxygen to 

 form hcematin in alkaline solution. Hoppe-Seyler, however, suc- 

 ceeded in obtaining the substance in crystalline form, by heating 

 haemoglobin with sodium hydrate solution in an atmosphere of hy- 

 drogen. In acid solutions ha3mochromogen gradually loses its iron 

 and is converted into hcematoporphyrin. In alkaline solution it 

 presents a beautiful cherry-red color, and on spectroscopic examina- 

 tion gives two bands of absorption. One of these is very intense, 

 and located between D and E, nearer D, while the other is not so 

 dark, but wider, and found about E and extending beyond b. To 

 demonstrate the spectrum of haemochromogen, bloody fluid is mixed 

 with a solution of sodium hydrate, when the resulting haematin is 

 reduced with ammonium sulphide, or Stokes reagent, viz., an am- 

 moniacal solution of ferrous tartrate, or stannous chloride. 



The haemochromogen radicle, as has been stated, represents the 

 pigmented group of the haemoglobin molecule, and to its presence 

 the power of haemoglobin to combine with oxygen, carbon dioxide, 

 and other gases, is unquestionably due. 



Hcemoglobin itself can be obtained in crystalline form, and is 

 characterized by the great resistance which it offers to putrefaction 

 and tryptic decomposition. It is stated that even after the lapse of 

 years decomposed blood contains its haemoglobin as such, and that 

 on shaking with air it may again be transformed into pure oxy- 



