IN THE ANIMAL KINGDOM. 25 



fact, as shown by the direct experiment of Henze with the blood of Octopus 

 vulgaris, it combines with only 0.4 c.c., which is less than two-thirds of 

 what it should be theoretically. The low O-capacity had been previously 

 determined by Dhe're in experiments with the bloods of Helix, Homarus, 

 Astacus, Octopus, Carcinus, Cancer, and Maia. Low figures have also been 

 recorded by others. 



From the foregoing it seems obvious that iron, manganese, or copper 

 is an incidental rather than the essential constituent of specific respiratory 

 substances, and that if there is a special constituent in relation to the prop- 

 erty of respiration it is as yet not definitely known. As a specific compo- 

 nent of these substances in relation to 0, the sulphur would seem to be of far 

 more importance than any of the metals named : its property as an ener- 

 getic oxidizing agent is universally recognized ; it is a universal constituent 

 of all proteins and hence of all protoplasmic structures, which structures 

 exhibit more or less absorptive activity towards O; the stromata of the 

 erythrocytes, globin, leucocytes, yeast-cells, etc., energetically decompose 

 peroxide of hydrogen. Especially energetic are the stromata of the eryth- 

 rocytes. The facts that about 96 per cent of the hemoglobin molecule is 

 protein, that stroma constitutes about 65 per cent of the erythrocyte, and 

 that the globin and stroma together represent about 95 per cent of the 

 erythrocyte of mammalian blood, strongly indicate a greater importance of 

 the protein than of the hematin, and especially so because the proteins show 

 affinities for and CO 2 , while the hematin is absolutely inert. The astute 

 Bunge long ago taught (Text-book of Physiological and Pathological Chem- 

 istry, trans, by Starling, 1902, 22; trans, by Wooldridge, 1890, 24) that the 

 respiratory function of hemoglobin can not be due to the iron alone and 

 that it may be that the sulphur of hemoglobin, as of all other protein 

 bodies, still retains its function as an oxidizing agent. In a very recent 

 article, Carracido (Rev. d. 1. R. Acad. d. Cienc., 1906, 33; Biochem. 

 Centralbl., 1906-07, v, 572) concludes that either the globin participates 

 in the oxygen absorption, or that the prosthetic group of chromoprotein 

 is not the conjectured one, since the sulphur-capacity of the hemoglobin 

 increases with the amount of oxygen absorbed. 



The assumption that the respiratory property of hemoglobin pertaining 

 to oxygen is essentially or solely a function of the atom of iron naturally 

 led as a corollary to a belief of an inertness or practical inertness of the 

 globin, and Bunge even suggested that "The enormous size of the hemo- 

 globin molecule finds a teleological explanation if we consider that iron is 

 eight times as heavy as water. A compound of iron which would float easily 

 along with the blood current through the vessels could only be secured by 

 the iron being taken up by so large an organic molecule." Bunge, later 

 in his lectures, still leans to the belief of the importance of sulphur, for he 

 states (loc. cit. 239) : 



If oxygen is chemically combined with hemoglobin, we would expect them to be 

 combined in molecular proportions. It would be interesting to ascertain how many 

 atoms of oxygen go to one atom of iron. The analyses made up to the present time are not 

 exact enough for this purpose; they show, however, that about 2 or 3 atoms of oxygen 



