'mi i \« l;i TION OP i i:l\T ;i \-< 



pressure equal to thai found in the aorta, a considerable flovi <.r fluid 

 maj I"' secured from the ureters, bul no fluid is obtained when tin- renal 

 portal vein is perfused ;ii a pressure equal to thai normally | J in 



this vein. Rowntree and Geraghty 11 found thai phenolsulphonephthalein 

 added to the perfusion fluid passed through the renal portal vein, «li«l nol 

 cause secretion, bul when urea was added to the perfusate, fluid con- 

 taining the dye was obtained from the ureter. Unfortunately tin- pi 

 sine employed in these experiments may have allowed some fluid to be 

 forced backward into the glomerulus, so thai the results may be due to 

 filtration through the capsule. 



Renal 

 artery 



■Malpighian 

 corpuscle 



Renal-portal vein 



Fig, \7.'. Diagram of blood suppl) I \l Ipighian corpuscle 



kidney. ( Redraw n I Cus 



It is generally accepted thai the proof thai the capsule acts as a fill 



is fairly < iplete. Unfortunately such decisive experimental facts can 



nol 1 ffered to prove the assumption thai the epithelium of the tubules 



reabsorbs the excess of water and salts which are filtered of? through 

 the capsule. It* the modern theory of urine excretion is i ells 



of the tubules musl nol only absorb large amounts of water, but they 

 must also allow for the reentrance into the blood, either complel 

 partially, of certain salts, while thej must reject others entirely. 



We have called attention above to the fad thai the glomerular filtrate is 

 very differenl from the urine thai is finally passed. The urine cont&ii 

 very high percentage of small molecules, and the proportion in which they 



