BLOOD. 215 



Although I cannot believe that this blood is entirely devoid 

 of separable fibrin, it certainly contains less fi])rin than arterial 

 blood. In fact it is more than probable that the quantity of 

 fibrin which is formed during the course of the blood through 

 the renal capillary system, where oxygen is taken up and not 

 again supplied, does not exceed the quantity consumed. Although 

 no determination of the hsematin and globulin was instituted, 

 we may infer, analogically, from our former analyses, and from 

 the necessary reciprocating proportions of the two principal 

 constituents of the blood, that less hsematoglobidin exists in the 

 blood of the renal veins than in that of the aorta. If the albu- 

 men in each be estimated in regard to equal quantities of the 

 solid residue, the albumen in the aortic blood will be found to 

 be to that in the blood of the renal vein in the ratio of 425 to 

 446. The quantities of haematoglobulin will therefore be in 

 an opposite ratio. 



These results throw considerable light upon the changes which 

 the blood undergoes in the kidneys. It loses a certain quantity 

 of water, which is accounted for bv the urine. Hence this 

 blood contains less water than the aortic blood. 



Urea appears to be formed from the corpuscles, under the 

 cooperating influence of the plasma and oxygen of the blood, 

 rather than from the albumen, which preponderates in the blood 

 of the renal veins the same as in the hepatic vein. It cannot 

 be positively asserted that the observations which were made 

 regarding the trifhng amount of fibrin in the blood of the he- 

 patic vein, as compared with that in the blood of the vena portse, 

 here hold good, but there are many reasons in favour of such 

 an analogous \'iew. 



It is highly probable that the activity of the excreting powers 

 of the kidney is due to the activity of the organ itself, as has 

 been already observed Avith regard to the liver, and that this 

 activity corresponds with the energetic evolution and revolution 

 of renal cells. 



That the kidneys do not separate bile, but urea, uric acid, 

 and salts, is due partly to the chemical constitution of the renal 

 cells and to the peculiarly directed cooperation of the nerves 

 of these organs, and partly, perhaps, to the composition of the 

 1)lood itself, which differs from that which supplies the liver. 



The separation of the water is caused by the peculiar internal 



