THE USE OF SOLUBLE PRUSSIAN BLUE 231 

 to the di-potassio-ferrous-ferrocyanide, 



- (cn \k 



Fe"< 



\CN), = Fe" 



In some cases the vessels of the animal or organ were, and 

 in other cases were not, washed out with warm normal saline 

 solution (75 per cent. NaCl). In some of the experiments, the 

 mixture was used in full strength, i.e. saturated solution of 

 soluble Prussian blue with 5 per cent, of gelatine added ; in 

 others it was diluted with an equal volume of 75 per cent. 

 NaCl. 



The apparatus I use consists of a very large glass bottle in 

 which water from the tap can accumulate and so raise the 

 pressure of the air above it, this pressure being recorded by a 

 manometer connected by a T-piece through the indiarubber 

 cork. 



The compressed air is driven over on to the surface of the 

 liquid blue gelatine in a WoulfPs bottle : this forces the material 

 out by a tube passing through the second aperture in the bottle 

 which leads to the cannula. When the whole animal is injected, 

 the cannula is inserted in the aortic arch as soon as the heart 

 ceases beating under deep chloroform anaesthesia. 



It is in the liver that the most energetic reduction of the 

 ferric to the ferrous salt seems to take place : on concluding 

 the injection under a pressure of 230 mm. of mercury in the 

 portal vein (the hepatic vein being tied), the lobes of the con- 

 gested liver present no green or blue appearance whatever, but 

 are of that grey-brown colour which they assume on having 

 had all their blood washed out. At the thin margins of some of 

 the lobes, the access of air here and there restores the colour. 



I have perfused the living kidney (pig, sheep, cat, rabbit) 

 both in situ and isolated from the body, and have not only found 

 the smaller vessels and capillaries filled with the leuco com- 

 pound which irrigation with H 2 2 immediately restores to 

 the blue condition, but have been able to induce an artificial 

 excretion of leuco gelatinous urine to drop from the ureter. 

 This material, on treatment with H 2 2 , became blue : on cutting 

 open the chilled, injected kidney after twenty-four hours, the 

 pelvis and calices were found filled with masses of absolutely 



