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A MANUAL OF PHYSIOLOGY 



blood-supply. The renal artery gives off afferent vessels to 

 the glomeruli ; the vena advehens, or renal portal vein, breaks 

 up, like the portal vein in the liver, into a plexus of capillaries 

 surrounding the tubules, and there seems to be no communication 

 between the two vascular systems. 



By tying all the arteries going to the kidneys in frogs the circu- 

 lation through the glomeruli can be completely cut off, while 

 ligation of the renal portal vein does not affect the blood-supply 

 of the glomeruli, though markedly interfering with that of the 

 tubules. Gurwitsch has found that after ligation of the renal 

 portal vein of one kidney in (male) frogs, the flow of urine from 

 that kidney is much diminished as compared with the other. 



He argues that if reabsorption 

 of dilute urine filtered through 

 the glomeruli takes place in the 

 tubules, the opposite result ought 

 to be obtained, since the glome- 

 ruli are not affected, while any 

 absorptive power of the tubules 

 must be crippled or abolished. 



In connection with the second 

 question, and also incidentally 

 with the first, the results of ex- 

 periments on the distribution of 

 pigments in the kidney after their 

 injection into the blood have of ten 

 been appealed to. Heidenhain in- 

 jected indigo-carmine into the 

 blood of rabbits, and after a 

 variable time killed them, cut 

 out the kidneys, and flushed 

 them with alcohol, in which the 

 pigment is insoluble. His results were as follows : (i) When the 

 spinal cord was cut before the injection in order to reduce the 

 blood-pressure, the blue granules were found in the ' rodded * 

 epithelium of the convoluted tubules and the ascending limb of 

 Henle's loop, and in the lumen of the tubules, but nowhere else. 

 Bowman's capsules contained no pigment. The renal cortex was 

 coloured blue. (2) When the spinal cord was not cut, the pigment 

 was found in the medulla and pelvis of the kidney, as well as in 

 the cortex, but always in the lumen of the tubules, and not in the 

 epithelium, except in the situations mentioned. (3) If a portion 

 of the cortex of the kidney had been cauterized with nitrate of 

 silver before injection of the pigment, the spinal cord being left 

 intact, a wedge of the renal substance, corresponding to this 

 area, remained coloured only in the cortex, although the rest 



FIG. 174. DIAGRAM OF DISTRIBU- 

 TION OF PIGMENT IN KIDNEY 

 AFTER INJECTION INTO BLOOD. 



The cortex between a and b and 

 between c and d was cauterized be- 

 fore the injection. In the black 

 wedge-shaped portions, i, there was 

 no pigment. In the zones shaded 

 like 2 there was some pigment, but 

 not so much as in the areas shaded 

 like 3. 



