PROTEINS 123 



iron. Oxygen forms with hemochromogen a more stable com- 

 pound than with hemoglobin. Hemochromogen shows character- 

 istic absorption bands. 



Hematoporphyrin. Hematoporphyrin is an iron free deriva- 

 tive of hemoglobin which may be prepared by adding blood to 

 concentrated sulphuric acid. The liquid becomes purple and may 

 be shown to contain hematoporphyrin. It gives two absorption 

 bands, one on each side of the D line. If the solution is made 

 alkaline, the acid hematoporphyrin is changed to alkaline hema- 

 toporphyrin, which shows a different spectrum. Hematopor- 

 phyrin is found in the urine in considerable amounts after sul- 

 fonal poisoning and the statement has been made that small 

 amounts occur in normal urine. Hematoporphyrin is interesting 

 from the fact that it is closely related to phylloporphyrin, a de- 

 rivative of chlorophyl, the green coloring matter in plants. In 

 this same connection it is also interesting that hematoporphyrin 

 acts as a photo-sensitizer, making animals sensitive to light. If 

 hematoporphyrin is injected into a white mouse, no ill effects ap- 

 pear so long as the animal is kept in the dark. If exposed to 

 strong sunlight, however, it will develop dyspnea, swelling of 

 the ears, edema of the skin, and ultimately will die. In man, in 

 some skin diseases connected with the action of strong sunlight, 

 hematoporphyrin has been observed in the urine. 



Fate of blood pigment in the body. Hemoglobin from broken 

 down corpuscles is converted into bile pigments, and thus is the 

 source of these coloring matters. The transformation in mam- 

 mals is made in the liver itself and undoubtedly to a considerable 

 extent in the spleen, although this latter organ probably carries 

 out only the first stages of the process. The bile pigments, bili- 

 rubin and biliverdin, and also urobilin, a yellow pigment in the 

 urine thus come from the broken down hemoglobin of the blood. 



Nucleoproteins. The nucleoproteins are found in the nuclei 

 of all cells, both plant and animal. It has been suggested that 

 they occur in other portions of the cell, or in the blood plasma, 

 but this is doubtful, although their decomposition products may 

 occur there. Since the cell nucleus is intimately concerned in the 



