CONDITION OF CO 2 IN THE BLOOD 155 



by its escape when the blood is placed in a vacuum. The total 

 amount escapes when the blood intact is placed in vacuo: when 

 the corpuscles alone are so treated they yield up all their CO 2 , 

 though it is small in amount ; but the plasma alone in vocuo yields 

 a less amount than when it contains corpuscles. If, now, corpus- 

 cles be added to the plasma the total amount of CO 2 is forth- 

 coming. The corpuscles must, therefore, act as an acid causing 

 the liberation of this gas from the plasma. It is probably the 

 hemoglobin, or oxyhemoglobin, which has this effect, though in 

 the laboratory the phosphates and certain proteids of the corpus- 

 cles produce a like reaction when brought in contact with the 

 carbonates and bicarbonates of soda. 



Condition of CO 2 in the Blood. About 5 per cent, of the 

 total amount of CO 2 in venous blood is in simple solution in the 

 plasma; about 75-85 per cent, is in loose chemical combination 

 in both corpuscles and plasma; the remaining 10-20 per cent, 

 is in comparatively stable combination in the plasma. Of the 

 75-85 per cent., by far the largest part is in the plasma, prob- 

 ably in a condition of loose association with sodium to form 

 carbonates and bicarbonates; the small part in the corpuscles 

 may exist in a similar state, but it is now thought to exist in com- 

 bination with the proteid portion of hemoglobin. The total 

 75-85 per cent, in corpuscles and plasma is so loosely combined 

 that the mere diminution in pressure in the lungs is probably 

 sufficient to liberate it. The 10-20 per cent, in firm chemical 

 combination is that part which cannot be extracted from plasma 

 alone in vacuo, but wh'ich is dissociated on the addition of an 

 acid, or corpuscles, or hemoglobin, etc. It may be that as the 

 blood passes through the lungs there is set free, in the formation 

 of oxyhemoglobin, an acid which immediately unites with the 

 bases holding the CO 2 in combination the liberation of the 

 latter being the consequence. 



The O being thus in the air vesicles, and the CO 2 thus free, or 

 set free, in the blood, with the very thin animal membrane con- 



