Chap, iv.] METABOLIC PROCESSES OF THE BODY. 583 



fering from those of blood-corpuscles on the one hand, and 

 from those of blood-serum on the other. But perhaps the most 

 striking feature of the spleen-pulp is its richness in the so-called 

 extractives. Of these the most common and plentiful are suc- 

 cinic, formic, acetic, butyric and lactic acids, inosit, leucin, 

 xanthin, hypoxanthin, and uric acid. Tyrosin apparently is 

 not present in the perfectly fresh spleen, though leucin is: both 

 are found when decomposition has set in. The constant pres- 

 ence of uric acid is remarkable, especially since it has been 

 found even in the spleen of animals, such as the herbivora, 

 whose urine contains none. 



The richness of the spleen in these extractives is an indica- 

 tion of the importance of the metabolic events with which the 

 organ has to do; but it will be more profitable to discuss what 

 goes on in the spleen in connection with the metabolic changes 

 in other parts of the body, in the liver for instance, than to 

 attempt to lay down any so-called ' functions ' of the spleen. 

 When we confine our attention to the spleen itself we learn 

 very little; thus the whole organ may be successfully removed 

 without any very obvious changes in the economy resulting. 

 We may return therefore to the discussion of the formation of 

 the bilirubin of bile, and of the changes undergone by haemo- 

 globin, with which as we shall see the spleen is connected, and 

 which moreover has to do with the formation of other pig- 

 ments. 



