766 



CHEMISTR Y OF RESPIRATION. 



that the gases of the blood were present in a state of loose chemical 

 combination with some unknown constituent of the blood, in a similar 

 way to that in which carbon dioxide is combined in solutions of sodium 

 phosphate. A few years later, Lothar Meyer l came to a similar con- 

 clusion, for he found that the amount of oxygen retained in the blood 

 only varied slightly with alterations of pressure. About the same time 

 Fernet 2 observed that the amount of oxygen chemically combined in 

 blood saturated with air was about five times greater than the quantity 

 which could be dissolved at the ordinary atmospheric pressure; this 

 oxygen was, moreover, chiefly contained in the red corpuscles. 



A further proof of the chemical combination of oxygen was obtained 

 when Bernard 3 and Hoppe-Seyler 4 discovered that the oxygen of the 

 blood could be displaced by an equal volume of carbon monoxide, a gas 

 which formed a more stable combination with the blood. The most con- 

 vincing proof, however, was furnished when Hoppe-Seyler succeeded in 

 crystallising hse.moglobin, and showed that it combined with oxygen, but 

 yielded up the gas to a vacuum ; he also showed that the haemoglobin, 

 for so he named the pigment of the red corpuscles, had a definite spectrum. 

 A year or two later, in 1864, Stokes 5 discovered that reducing sub- 

 stances removed oxygen from the haemoglobin and effected a marked 

 change in its colour and spectrum. 



The physical and chemical properties of haemoglobin are described 

 fully in another part 6 of this work ; here it is only necessary to discuss 

 the part which the pigment plays in the processes of respiration. 



The coefficient of absorption of blood for oxygen is a little lower than 

 that of water, for the presence of salts in solution diminishes the capacity 

 of the liquid to absorb gases. 7 The following table shows the volume of 



1 "Die Gase des Blutes," Diss., Gottingen, 1857 ; Ztschr. f. rat. Med., Bd. viii. S. 256. 



2 A nn. d. sc. nat.,- Paris, 1857, Se"r. 4, Zool., tome viii. p. 125; Journ. de physiol. 

 exp6r., Paris, 1860, tome iii. 



3 "Lecons sur les effets des substances toxiques et medicamenteuses," Paris, 1857, p. 

 184 ; "Lemons sur les liquides de 1'organisme," Paris, 1859, tome i. p. 365 ; tome ii. p. 427. 



4 Virchow's Archiv, Bd. xi. S. 288 ; Bd. xiii. S. 104. 



5 Proc. Roy. Soc. London, vol. xiii. p. 357. 



6 Article " Haemoglobin, " this Text-book, vol. i. 



7 Mackenzie, Ann. d. Phys. u. Chem., Leipzig, 1876, Bd. i. S. 438 ; Setschenow, Ztschr. 

 f. physical. Chem., Leipzig, 1889, Bd. iv. S. 117; Hlifner, Arch. f. Physiol., Leipzig, 

 1894, S. 130 ; 1895, S. 209. 



8 Ann. d. Chem. u. Pharm., Bd. xciii. S. 1 ; "Gasometrische Methoden," Braunschweig, 

 1857, S. 136. 



9 Ztschr. f. physical. Chem., Leipzig, 1892, Bd. ix. S. 174. 



10 Ann. d. Phys. u. Chem., Leipzig, 1876, Bd. i. S. 632; Arch. f. Physiol., Leipzig, 

 1890, S. 27. 



