160 CIRCULATING FLUIDS: 



In these cases there is, therefore, not merely a diminution of 

 the quantity of the blood-corpuscles, but likewise of the colouring 

 matter contained therein, since the corpuscles that remain are 

 young and deficient in colouring matter, containing, in addition 

 to hsematin, only a very small quantity of hsemaphsein. If the 

 cu'culation of the blood is impeded in any part of the body, and 

 it is prevented from receiving its due supply of oxygen, the 

 metamorphosis will likewise be impeded and rendered imperfect ; 

 the matured blood-corpuscles which are approaching the stage 

 of solution wiU not be dissolved, and there will consequently 

 be an accumulation of colouring matter, especially of hsema- 

 phaein, which is the most abundant pigment in the matured 

 corpuscles. 



All these appearances are actually observed. I shall be able 

 to demonstrate that, in inflammatory affections, (when the me- 

 tamorphosis of the blood is excited to increased activity in con- 

 sequence of the accelerated circulation and the increased mutual 

 action of the blood and oxygen,) there is only a small amount 

 of colouring matter present in the blood, and that, in all pro- 

 bability, hsemaphsein constitutes but a minute portion of the 

 little that does exist ; while, on the other hand, in blood which 

 is retained in the body without being submitted to the due 

 action of oxygen, in which the perfect metamorphosis is checked, 

 and the corpuscles are not dissolved, as in melsena and in 

 morbus maculosus, there is a great excess of hsemaphsein. The 

 coloui'ing matter may also accumulate when organs that take an 

 active part in the metamorphosis of the blood are affected, as 

 I have observed in morbus Brightii. 



I shall now proceed to show that it is much more probable 

 that such substances as urea, uric acid, and bilin, which are 

 definite compounds secreted in a nearly constant ratio by peculiar 

 organs, should be products of the active metamorphosis of the 

 blood-corpuscles, than that they should be formed diu-ing the 

 metamorphosis of the plasma in connexion with the process of 

 nutrition. 



It is but reasonable to infer that such substances as urea, 

 Miic acid, and bilin, which are separated in large quantity by 

 the kidneys and liver from the blood, should be products of the 

 metamorphosis of a substance of an invariably uniform compo- 

 sition. In every class of animals, in the most varied forms of 



