768 CHEMISTR Y OF RESPIRA TION. 



of oxygen for 1 grm. of haemoglobin. The usual form of haemoglobin is 

 /-haemoglobin ; this, when dried, gives a crystalline powder, a-haemo- 

 globin, which in turn yields, on solution in water, /3-hsemoglobin. A 

 solution of /-haemoglobin, when kept in a closed tube, is converted 

 into ^-haemoglobin. These various kinds of haemoglobin have different 

 " specific oxygen capacities," by w T hich term Bohr designates the ratio 

 between the number of grammes of iron and the number of cubic 

 centimetres of oxygen present in a given volume of blood, of blood 

 corpuscles or solutions of haemoglobin, saturated with air at ordinary 

 pressure and temperature. The red blood corpuscles are said to 

 undergo alterations in their specific oxygen capacity during their 

 passage through the circulation. 



These results and theories have been subjected to an experimental 

 examination by Hiifner, 1 who maintains that in fresh, healthy ox-blood 

 there is only one kind of haemoglobin, that the capacity of the fresh 

 haemoglobin for carbon monoxide and for oxygen is the same, whether 

 it be haemoglobin directly dissolved from red corpuscles or haemoglobin 

 first crystallised and then dissolved in water. By experiment, Hiifner 

 shows that 1 grm. of haemoglobin takes up T33S c.c. of carbon monoxide 

 or oxygen measured at and 760 mm. This is confirmed by the 

 following facts. The capacity of haemoglobin to combine with oxygen 

 appears to depend upon its iron, one atom of which holds two atoms of 

 oxygen. The haemoglobin of ox-blood contains 0'336 per cent, of iron, 

 and its molecular weight is 16,669 ; its capacity for carbon monoxide or 

 oxygen, as calculated from its percentage of iron, is T34 c.c. for 1 grm., 

 a figure practically identical with that obtained by direct experiment. 2 

 This is probably also the case with haemoglobin obtained from the 

 horse, dog, pig, rabbit, and fowl, for Bunge and others 3 have shown 

 that the general percentage of iron is O335 per cent. Further, the 

 amount of haemoglobin in human blood is about 14 per cent., and since 

 1 grm. of haemoglobin can absorb about 1 '34 c.c. of oxygen, it follows that 

 the amount of oxygen combined in arterial blood should be about 20 

 volumes per cent., and actual experiment shows that this is the case. 4 



It is probable that some of Bohr's results are due to mixtures of 

 pure and partly decomposed haemoglobin, and that some of the haemo- 

 globin may be in the form of methaemoglobin. The same criticism 

 may possibly apply to the results obtained by Haldane and Lorrain 

 Smith. 5 



The oxygen in the blood of invertebrates. In many of the invertebrate 

 animals, haemoglobin, haemocyanin, and other proteids, which can enter into 

 loose combination with oxygen, are found and play a part in the process of 

 respiration. It is impossible, however, in a few words, to do justice to this 

 interesting portion of comparative physiology ; for further details, the article 

 by Halliburton 6 on the blood of invertebrate animals should be consulted. 



1 Arch.f. PhysioL, Leipzig, 1894, S. 130. 



2 See also Hoppe-Seyler, Virchow's Archiv, Bd. xxix. S. 598; Med.-chem. Untersuch., 

 1867, Bd. ii. S. 191 ; Preyer, "De hsemoglobino observation es et experimenta, " Bonnse, 

 1866, p. 19 ; GentralU.f. d. med. Wissensch., Berlin, 1866, No. 21. 



3 Jaquet, Ztschr. f. physioL Chem. , Strassburg, 1889, Bd. xiv. S. 289. 



4 See p. 761. 



5 Journ. PhysioL, Cambridge and London, 1894, vol. xvi. p. 468. 



6 "Text-Book of Chemical Physiology and Pathology," London, 1891, pp. 316-330. Here 

 numerous references to previous work on the subject will be found. Among subsequent 

 papers may be mentioned those of Griffiths, Compt. rend. Acad. d. sc., Paris, 1892, 

 tome cxv. pp. 259, 419, 474, 669, 738 ; cxvi. p. 1206. 



