12 



PHYSIOLOGY OF NUTRITION 



of animal blood. Hematoporphyrin has the composition CieHigNaOs, the dif- 

 ference between it and phylloporphyrin, as represented by these formulas, con- 

 sisting in the lower oxygen content of the latter.^ The method used in the 

 isolation of hematoporphyrin is also analogous to that employed for phyllopor- 

 phyrin. The spectra of these two substances, in various solvents, ^ are almost 

 identical, except that the absorption bands of hematoporphyrin sometimes 

 appear slightly displaced toward the red (Fig. 7). 



Both hematoporphyrin and phylloporphyrin, when heated in a test-tube, 

 form a vapor which gives a red color to pine sawdust moistened with hydro- 

 chloric acid, a characteristic indication of the presence of the pyrrol ring 

 (C4H6N): the characteristic odor of pyrrol may also be plainly recognized in 

 this vapor. ^ It thus appears that chlorophyll (acting synthetically) and hemo- 

 globin (acting analytically) are closely related, in that the pyrrol ring is common 

 to both. It is of great interest also to note that the bile pigment bilirubin 

 has the same percentage formula as hematoporphyrin (CieHisNaOs). Further- 

 more, Nentskii and Zaliesskii* succeeded in obtaining mesoporphyrin from hemin, 

 the latter substance being formed by the action of acids upon hemoglobin. 

 Mesoporphyrin has the composition C16H18N2O2, and stands between hemato- 

 porphyrin and phylloporphyrin in oxygen content. By a further decomposition 

 of hemin these authors obtained hemopyrrol (CisHgN), a volatile oil that turns 

 red in air and changes into urobilin, which is also obtained from bilirubin. 

 When Nentskii and Marchlewski^ succeeded in obtaining hemop)Trrol and 

 urobilin from phylloporphyrin, the relationship between chlorophyll and 

 hemoglobin was conclusively established. The atomic group common to 

 both, as in the case of the bile pigments, occurs in hemopyrrol. The following 

 diagram represents the relationship existing between these three groups of 

 substances. 



Chlorophyll 

 Phylloporphyrin 



Hemoglobin 

 Hematoporphyrin 



Hemopyrrol 



Urobilin 



. I 



Bilirubin 



1 For the difference in structure between the two compounds see: Willstatter, Richard, and Asahina, 

 Yasuhiko, Oxydation der Chlorophyllderivate. Liebig's Ann. Chem. u. Pharm. 373: 227-238. 1910. 



2Schunck, E., and March lewski, L., Zur Chemie des Chlorophylls. (Vierte Abhandlung!) Liebig's 

 Ann. Chem. u. Pharm. 290: 306-313. 1896. 



» Schunck, E., and Maichlewski, L., Zur Chemie des Chlorophylls. (Dritte Abhandlung.) Liebig's 

 Ann, Chem. u. Pharm. 288: 209-218. 189s. ■ 



« Nencki, M., and Zaleski, J. Ueber die Reductions producte des Hamins durch Jodwasserstoff and 

 Phosphomumjodid und uber die Constitution des Hamins and seiner Derivate. Ber. Deutsch. Chem. Ges. 

 34^: 997-1010. 1901. 



•Nencki, M., and Marchlewski, L., Zur Chemie des Chlorophylls. Abbau des PyhUocyanins zura 

 Hamopyrrol. Ber. Deutsch. Chem. Ges. 34 ': 1687-1693. 1901. 



