136 Journal of the Asiatic Society of Bengal. [N.S., XVI, 
(2) Reversal of the Current of ne fluid through the Kidney. 
In nine experiments (five on the frog and four on the 
rabbit—vide Appendix H) | sareitty compared the results of 
perfusing the kidney via the renal arteries (the ordinary direct 
current) and perfusing in the reverse direction, i.e. in at the 
renal veins and out by the renal arteries. In the case of the 
frog I perfused 0°6% saline plus 0°05% urea at 24 cms. pres- 
sure at room temperature first through the aorta (the systemic 
and iliac arteries and the renal afferent veins being ligatured) 
and then through the post- are (the renal arteries being cut) at 
the same pressure. In the case of the rabbit I perfused 0°9% 
saline plus 100 c.c. fresh human urine added to each 2,000 c.c. of 
the saline at 100 cms (water) pressure at about blood tempera - 
ture first through the renal arteries of both kidneys and then 
through the renal vein of one kidney, the other kidney continuing 
as before as acontrol. In the first frog experiment the reverse 
current (R.C.) gave eight times the amount of urine obtained by 
the ordinary direct current (D.C.) in coat same time and of a nitro- 
gen strength of 0-000140 gm. per 1 c.c. as compared with the 
0:000193 gm. of the direct current (the sectiaua fluid was of a 
nitrogen strength of 0-000153 gm. ). In the second frog experi- 
ment R.C. gave 8°5 times more urine than D.C. the R.C. urine 
nitrogen strength being 0-000153 gm. and_ chloride (as 
NaCl) strength being 0:006154 gm., as compared with the D.C. 
urine nitrogen strength of 0- 000215 gm. and chloride strength 
of 0°005406 gm. Hence, as usual, the increased pressure in 


wholly Bea ae to the nature of the fluid aid perfusing its a. or 
capillaries. t this is mS When the blood in a living animal con- 
cess ps tc the first thing - kidney does is to ‘get rid of “the 
depends upon no such special chemical m s and its activity xe 
st aa Biotic by the nate of the i heen: fuid. which, to it, is 
sufficient indication of the needs of the body. 
To zie emn saline perfusion experiments on the mammal’s kidney, 
e.g. on the ground that it is necessarily dead under these conditions is 
an argument only rendered possible by the fact that cs verybody’s 
mind is obsessed by the idea of Fe ates r filtration. Glandular epithelium 
in general (including that of the tubules) is pyres develo oped when secretion 
occurs (ie. when the substances extracted from the blood a differ in con- 
centration from those in the blood, and perhaps also when only a selec 
yo is made) but this does not inhibit, glandular epithelium playing more 
t less the part of a filter when conditions demand that it should. 
