192 BLOOD. 



established facts. Marchand believed that if blood containing no 

 carbonic acid produces no carbonic acid by the direct influence of 

 oxygen, the oxygen can only be mechanically absorbed : now he 

 found, in point of fact, that fresh blood after its carbonic acid had 

 been removed, was as incapable of developing the slightest trace 

 of carbonic acid, when a stream of oxygen was passed through it, 

 as the serum of the blood, egg-albumen, solutions of blood-cor- 

 puscles, &c., when similarly treated ; but independently of the 

 circumstance to which we have already referred, that van Maack 

 and Scherer have actually observed the exhalation of carbonic 

 acid from heematin after its previous absorption of oxygen, nothing 

 more is proved by Marchand's experiment than that oxygen can 

 be absorbed by the blood without giving rise to the formation of 

 carbonic acid ; but it is still quite possible that one or other of the 

 constituents of the blood becomes more highly oxidised without 

 any separation of carbonic acid, since a development of this gas 

 does not of necessity follow every oxidation of an organic body. 

 The mode of calculation adopted by Magnus, would be more con- 

 vincing, were it not that the numbers on which it is based, rest on 

 too uncertain determinations. If, for instance, about 13 Paris cubic 

 inches of oxygen make their way into the blood of an adult man in 

 one minute if, further, about 10 pounds of blood pass through the 

 lungs in the same interval then, considering that about 11 of 

 oxygen are found in the blood of the horse, it follows that about 

 half the oxygen which Magnus found in arterial blood has been 

 absorbed from the venous blood, so that, according to this, the 

 former would always lose about half its free oxygen in the capillaries. 

 The preceding statement and the above-mentioned facts afford a 

 sufficient proof that the greater part of the oxygen absorbed in the 

 lungs, exists in a state of freedom in the blood ; but it seems to us 

 not at all indubitably established that no portion whatever of the 

 absorbed oxygen enters into chemical combination with one or 

 other of the constituents of the blood, even in the heart and 

 arteries, since such a combination is believed to take place in the 

 capillaries. 



In every case the relation of the gases to the blood-corpuscles 

 must be accurately determined by special experiments before a 

 definite view can be formed on the subject. 



Before we proceed to the more minute consideration of the 

 intercellular fluid, we must make mention of certain morphological 

 elements which, in addition to the coloured cells, are found sus- 

 pended in the blood : these are the colourless corpuscles to which 



