174 On Absorption. 



enormous quantity of bright blue particles. Another portion 

 of the urine was taken, and evaporated in a white porcelain 

 dish ; towards the end of the process a dirty blue residuum 

 was formed ; to this distilled water was added, and gentle 

 heat of a warm-bath applied. Much organic matter was 

 thus removed, the residuum having all the appearance of 

 Prussian blue. Examined with the microscope there were no 

 longer the doubtful crystals, but true amorphous piussian 

 blue. 



Seven hours after, more urine just passed was examined, 

 but not a trace of either the ferrocyanide or iron was 

 detected, and upon evaporation no prussian blue was 

 obtained. 



Thus, then, in twenty-four hours were the kidneys enabled 

 to retnove this large amount of iron and potash from the 

 body ; a result agreeing with %vhat we saw in the last expe- 

 riment with the cock, and with all the previous ones with the 

 aniline dyes. 



Experiment 3. — ^Three days after this, the dog being per- 

 fectly well, on again tapping the abdomen, I drew off some 

 serum slightly tinged with blood. In this I sought to detect 

 some of the iron I had three days previously injected ; not a 

 trace was discovered. I again threw in one and a-half ounce 

 of solution, perchloride of iron, raised to 100°F., and one and 

 a-half ounce of a saturated solution of ferrocyanide of po- 

 tassium of the same temperature. The former into the 

 peritoneum, the latter beneath the skin of the back. 



During the succeeding twelve hours, the blood yielding 

 crystals as before, the urine was several times examined, 

 giving still more abundant evidence of the presence of 

 the ferrocyanide, but not of the iron, until evaporation, 

 when the residuum being washed, prussian blue, this time 

 in great quantity, was obtained. Besides the peculiar colour 

 of prussian blue, and its amorphous appearance beneath 

 the microscope, the residuum behaved as follows : — 



1st. Insoluble in water. 



2nd. Colour destroyed by sulphuric acid, and reproduced 

 on the addition of water. 



3rd. Both potash and soda bleached it, but the colour re- 

 appeared on the addition of either sulphuric or hydrochloric 

 acid. 



4th. Oxalic acid changed it to a most beautiful blue, but 

 failed to dissolve it, probably owing to the organic matter 

 with which it was, doubtless, still combined. 



