BLOOD. 155 



c. The consumption of oxygen and the formation of carbonic 

 acid stand in a direct ratio with the amount of ])lood-corpuscles, 

 and with the number of respirations in a given period. 



Hence it is obvious that the oxygen taken up by the blood 

 diu-ing the respiratoiy process, is, for the most part, consumed 

 in the metamorphosis of the corpuscles. i 



The development of the blood-corpuscles is doubtless con- 

 ducted on the same principle as that of other cells ; i. e. the 

 blood-corpuscles exert a transforming influence on the surround- 

 ing plasma ; they select from it the materials requisite for their 

 development, and reject the non-homologous products that are 

 formed in it. Amongst the matters that are taken up there 

 must be always free oxvgen. 



During the later stages of development of the blood-corpus- 



' [There are two rival theories respecting the manner in which oxygen is taken up 

 by the blood and conveyed to the peripheral system. Liebig maintains that this is 

 effected solely by the iron in the corpuscles, while Mulder refers it entirely to the oxi- 

 dation of protein-compounds. Liebig asserts that the coriniscles of arterial blood con- 

 tain peroxide of ii'on ; that, in their passage through the capillaries, they lose a portion 

 of their oxygen and combine with carbonic acid, so that, in the venous system, they 

 no longer contain peroxide, but carbonate of the protoxide of iron. When they reach 

 the lungs, an exchange takes place between the carbonic acid of the blood and the 

 oxygen of the atmosphere. Mulder, on the other hand, denies that the blood -cor- 

 puscles are conveyers of oxygen, and that iron is oxidized dming respiration, as 

 assumed by Liebig, and he found his conclusions on the following grounds : 



a. The iron is so intimately connected with the other elements of hajmatin that 

 it cannot be removed, even by long digestion of this constituent in dilute hydrochlo- 

 ric or sulphuric acid. (Vide supra, p. 41.) Consequently it is highly improbable 

 that it should be oxidized in the lungs. Liebig, indeed, obsen^es that dilute acids 

 remove iron from dried blood, but Mulder gets over this difficulty by showing that 

 other constituents of the blood, besides the colouring matter, contain this metal, 

 apparently in an oxidized state. 



(i. If, as Liebig asserts, peroxide of iron exists in arterial, and carbonate of prot- 

 oxide of iron in venous blood, almost any dilute acid would be capable of extracting 

 the oxide, which we have shown not to be the case. 



y. Assuming, with Liebig, that the iron exists in arterial blood as a peroxide, 

 the organic part of haematin would be different ; instead of being C44 H02 N^ Og, it 

 would be 2 (C, H,, N3 Og Fe) - Fe, O3, or 2 (C,, II,, N3 0,.^. 



S. The probability of its existence in a metallic state has been already shown. 

 (Vide supra, p. 42.) 



t. The amount of haematin in the whole mass of the blood is far too inconside- 

 rable to carry a due supply of oxygen to the whole system. 



Mulder's theory has been alluded to in an early part of this work. (Vide supra, 

 p. 12, note.) We shall have occasion to notice it at some length in our obsenations 

 on the differences between ai"terial and venous blood.] 



