504 CHEMISTRY OF THE PROTEIDS CHAP. 



consequent paralysis of the oxygen-carrying power of the blood. In 

 compressed oxygen this action is abolished, and with very large doses 

 nitrites then act as direct poisons to the tissues. Nitroglycerine, 

 nitrobenzene, and hydroxylamin act in mice and rabbits as direct 

 tissue poisons before producing symptoms due to the decomposition of 

 the hemoglobin or to nitrite formation. Dinitrobenzene decomposes 

 the haemoglobin into a product which is incapable of carrying oxygen. 



Sulph-hsemoglobin 



Hoppe-Seyler l first observed that by the action of H 2 S on oxy- 

 hemoglobin the haemoglobin molecule is destroyed, there being formed 

 a greenish compound which Araki 2 has called sulpho-methemoglobin. 



He' also described a true sulph-hemoglobin with higher sulphur- 

 contents and with an absorption-band in the red, 3 but the real 

 explanation we owe to Harnack. 4 By the action of H 9 S on reduced 

 haemoglobin, sulph-hemoglobin is said to be formed, but it has not as 

 yet been prepared in a pure state. It exhibits the absorption-band 

 of reduced hemoglobin in the green, but in addition a distinct band 

 in the orange-red, between C and D, but nearer to C, without, however, 

 reaching this line ; it lies therefore considerably more towards the 

 violet end than do the bands of methemoglobin or of hematin. On 

 converting hemoglobin into sulph-hemoglobin the solution becomes of a 

 darker red. Harnack proved thatwe are really dealing with a compound 

 of hemoglobin with H 2 S, and that neither * acid-hemoglobin ' (see 

 p. 495) nor methemoglobin give rise to sulph-hemoglobin. Whether 

 hemoglobin can be regenerated from its H 2 S compound could not be 

 determined, but is probable. If H 2 S acts on oxy hemoglobin or on 

 hemoglobin in the presence of air, there is also formed at first sulph- 

 hemoglobin, but this is succeeded by a complete decomposition of the 

 hemoglobin, leading to complete disappearance of all typical absorp- 

 tion-bands of hemoglobin. Araki failed also in obtaining normal 

 hematin. The decomposed solution is of a dirty greenish colour, 

 but the latter does not depend on any definite coloured substance. It 

 has been suggested that the decomposition is due to rapidly alternat- 

 ing processes of oxidation and of reduction, owing to the combined 

 action of 2 and H 2 S. (Cohnheim.) 



1 F. Hoppe-Seyler, ZentralbLf. d. med. Wissensch. 1863, Nr. 28. 



2 Trasaburo Araki, Zeitschr. /. physiol Chem. 14. 405 (1890). 



3 F. Hoppe-Seyler, Med.-chem. Untersuchungen, p. 151 (1866). 



4 E. Harnack, Zeitschr. /. physiol. Chem. 26. 558 (1899). 



