138 SANGUIFICATION. L.ECT. VII. 



peroxide, and sometimes as a carbonate [of the protoxide,] 

 must have some influence in effecting the change of colour. 

 In fact, oxygen, expels carbonic acid from carbonate of 

 iron, while carbonic acid replaces the oxygen of the peroxide, 

 according to the relative proportions of oxygen and carbonic 

 acid present. 



Mulder and Liebig appear to have adopted these opinions. 

 All the best established clinical results apparently prove that 

 the use of iron in certain maladies restores in some way the 

 colour of the blood. Nevertheless, Scherer has recently 

 satisfied himself that he obtained the colouring matter of 

 the blood entirely free from iron. If Scherer's observation 

 be ultimately confirmed, and if, moreover, it be proved that 

 this colouring matter, deprived of iron, undergoes, by con- 

 tact with oxygen and carbonic acid, the changes which we 

 have seen take place in the blood globules, we shall be 

 compelled to give up the idea that iron intervenes in the 

 change of the colour of the blood. 



Conversion of arterial into venous Blood. The arterial 

 blood, propelled by incessantly renewed contractions of the 

 heart, as well as by the successive dilations and contractions 

 of the coats of the arterial vessels, owing to their peculiar 

 elasticity, arrives with this red colour in the last capillary 

 ramifications. Still contained in these vessels, it traverses 

 all the tissues, loses its red colour, and returns by the veins 

 to the heart in order to pass again into the lungs. 



Renovation of the Tissues. Physiologists tells us that 

 nutrition takes place during the passage of the arterial blood 

 through the capillaries. They assume that every portion 

 of the animal tissues is incessantly renewed and transform- 

 ed ; and that these phenomena vary in intensity, and are 

 proportionate to the different degrees of activity of the 

 capillary systems of the different tissues. In truth, experi- 

 mental evidence of this renovation is still wanting; and that 



