RESPIRATION. 365 



physical absorption. The indications are that it partakes of the 

 nature of a chemic combination. 



If the red corpuscles be removed from the blood and the plasma 

 alone be treated in the manner above described, it will be found that the 

 oxygen liberated now follows the law of partial pressure. The amount 

 so liberated, however, is small about one per cent, of the total oxygen 

 of the blood. The agent therefore which holds the oxygen in com- 

 bination is the red corpuscle, and more especially the hemoglobin, 

 which constitutes about 94 per cent, of its volume. This is proved by 

 the fact that a solution of gas-free hemoglobin of a strength equivalent 

 to that of the blood (14 per cent.), exposed to gradually increasing 

 pressures from zero up to 30 or 40 mm. oxygen pressure, will absorb 

 large quantities of oxygen; beyond this point the amount absorbed 

 is again small in comparison. At 70 mm. pressure the hemoglobin 

 is almost saturated. Coincidently with this absorption the hemo- 

 globin changes in color from dark blue to bright red; changes from 

 hemoglobin to oxyhemoglobin. The reverse method, that of subjecting 

 oxyhemoglobin to gradually diminishing pressures, yields opposite 

 results. As one gram of hemoglobin combines with 1.59 c.c. of 

 oxygen, anoT as TEe/percentage oi hemoglobin is 13.50 to 14, it is 

 evident th&t there is sufficient hemoglobin to CUlliblim Wiln practically 

 all the oxygen usually present in tne PJOOQ. 



The relation of the oxygen in the blood is therefore partly physi- 

 cal, partly chemical. One per cent, is physically absorbed by or 

 dissolved in the plasma; the remainder is chemically combined with 

 the hemoglobin. 



The association or combination of oxygen is favored by a pressure 

 of at least from 30 to 50 mm. Hg and upward; the dissociation, by 

 diminution of pressure. -^-In the conversion of hemoglobin into oxy- 

 hemoglobin twoantagonistic forcesare at work, heat and chemic 

 affinity. The ^former ^endeavors to prevent, the latter to favor, 

 the union. Chemic affinity increases with the influence oTrnass/that is, 

 in proportion to the number of atoms in a unit of volume, with the 

 density and with the partial pressure of the oxygen. Diminution of 

 pressure reduces the mass influence and permits the heat to bring 

 about dissociation (Bunge). The following table by Hiifner shows 

 the relative proportion of hemoglobin and oxyhemoglobin in blood 

 containing 14 per cent, hemoglobin and exposed to air at gradually 

 diminishing pressures : 



ATMOSPHERIC PRESSURE PARTIAL PRESSURE OF HEMOGLOBIN OXYHEMOGLOBIN 



IN MM. Hg. OXYGEN IN MM. Hg. PERCENTAGE. PERCENTAGE. 



760 159.3 x -49 9 8 -5 J 



524.8 no 2.14 97.86 



357-8 75 3.11 96-89 



238.5 50 4.60 95.40 



1193 25 8.79 91.21 



47.7 10 19-36 80.64 



23.8 5 32.51 67.49 



O.O O.O IOO.OO O.OO 



