BLOOD. 219 



of the organism, and for this purpose the circulating fluid is 

 modified and consimied in the peripheral system. AVc have 

 conjectm'ed that the extractive matters of the blood Mhich are 

 removed by the kidneys are thus formed. The constant mo- 

 dification and consumption of blood dependent on the act of 

 nutrition render the supply of fresh nutrient fluid, and the re- 

 moval of efl'ete matter, indispensably necessary, since a proper 

 constitution of the blood is requisite for the due performance 

 of the function of nutrition. The efl'ete matters are replaced 

 by chyle mixed with hTnph ; and this fluid must of necessity 

 be converted into blood, as otherwise the blood would soon 

 consist entirelv of chvle. The change is eff"ected bv the for- 

 mation of yoimg blood-corpusles, (an act which is accompanied 

 by the consumption of chyle-, lymph-, and oil-corpuscles,) and 

 by the fibrin of the chyle becoming more plastic ; all the other 

 fluid constituents of the chyle are similar to those of the liquor 

 sanguinis, except that there is an excess of water and of ex- 

 tractive matters in the former. If therefore we suppose a con- 

 tinuous fonnatiou of blood-coi'puscles, the necessity for their 

 consumption must be sufficiently ob\'ious. I have assumed that 

 fibrin is formed as a consequence of this consumption, and that 

 this newly-formed fibrin supplies the place of that which is em- 

 ployed for the purposes of nutrition in the peripheral vascular 

 system. I have also shown, (page 163,) that there is no diffi- 

 culty in the idea of the formation of albumen; and lastly, I 

 attempted to show that, in all probability, ui'ca, ui'ic acid, and 

 bilin are formed as a consequence of this consumption of the 

 blood-corpuscles. For these substances must necessarily be 

 formed as products of the changes wliich the constituents of the 

 blood undergo in the circulation, and are not (as observations 

 on starved and emaciated individuals show us) a consequence of 

 the changes which the circulating fluid undergoes during the nu- 

 trition of the tissues, but are dependent on the metamorphic 

 action that is produced by the respiratory process. It is prin- 

 cipally the blood-coi'puscles, (as I have endeavoured to show, in 

 page 155,) that are connected with the consumption of oxygen; 

 and when we reflect that this change in the corpuscles must 

 take place under similar conditions in animals both high and 

 low in the scale of development, we can understand how it is 

 that urea, uric acid, and bilin occur in the renal and hepatic 



