102 COMBINATION OF O 2 WITH HAEMOGLOBIN. [BOOK I. 



The facts which have been narrated above supply the chief 

 materials for forming an opinion in reference to the nature of the 

 compound of haemoglobin with oxygen. From them it would appear 

 that this compound is of so remarkable a nature that it may be 

 formed with exceptional facility by the mere contact with atmospheric 

 oxygen, and that it is one which readily undergoes dissociation the 

 decomposition being one in which the molecule of haemoglobin is left 

 intact and ready to combine again with fresh molecules of oxygen. 



What is the quantity of oxygen which reduced 

 of the'reap*- haemoglobin can link to it as respiratory oxygen ? 

 ratory or Preyer 1 as a result of three determinations found 



loosely com- that 1 gramme of haemoglobin can link to itself 1'27 

 Dined oxygen cu ^ cents, of oxygen measured at C. and 1 metre 

 mog^obin 6 ' pressure (or 1*671 c. c. measured, as is more usual in 

 England and France, at C. and 760 mm. pressure), 

 and more recently Hufner 2 has determined the amount again by a 

 different method and has obtained a result almost identical with that of 

 Preyer. According to Hufner and as the mean of ten separate deter- 

 minations, 1 gramme of haemoglobin fully saturated with oxygen is 

 associated with T28 c.c. of oxygen gas (measured at 0C. and 1 

 metre pressure.) 



Dissocla- Oxy-haemoglobin is one of those compounds which at 



tion-tension particular temperatures and pressures undergo dissociation. 

 of the respi- At 40 C. the dissociation-tension is equal to about 30 mm. 

 ratory oxygen of mercury 3 . The Author attempted some time ago to ascer- 

 of oxy-hae- tain the dissociation-tensions of oxy-haemoglobin for various 

 moglobin. temperatures, but the results which he obtained were not 



sufficiently accordant to allow of conclusions being drawn from them. The 

 subject will be discussed again under ' Respiration.' 



Before leaving this division of our subject we have 

 oxy^aemo- * re ^ er to a reaction which is possessed by oxy- 

 giobin upon haemoglobin and by some of its derivatives, though not 

 the resin of by reduced haemoglobin, and to which at one time con- 

 Guaiacum. siderable theoretical importance was attached, and which 

 still is of great practical value inasmuch as it affords us the most 

 delicate, though by itself not a conclusive, test for detecting exceedingly 

 minute quantities of these bodies. 



It was found by A. Schmidt that when diluted blood is dropped 

 upon a filter paper which has been moistened with tincture of 

 guaiacum and then dried spontaneously in the air, a blue ring forms 

 at the edge of the drop ; it is best in this experiment to use blood 

 diluted with 20 times its volume of water, and it may be well to 

 remember that the reaction is one which is not produced by all 



1 Preyer, Die Blutkrystalle : Untersuchungen von W. P., Jena, 1871, p. 134. 



2 Hufner, " Ueber die Quantitat Sauerstoff welche 1 Gramm Hamoglobin zu binden 

 vermag." Zeitschriftf. physiologischen Chem. Vol. i. p. 317. 



3 Worm Miiller, "Ueber die Spannung des Sauerstoffs derBlutscheiben." Ludwig's 

 Arbeiten, 1870, p. 119. 



