On Absorption. 175 



Twelve hours after a large quantity of paler urine was 

 passed, in which not a trace of either salt injected was 

 discovered. 



Forty-eight hours after the dog had been first injected it 

 was killed. 



There were about two ounces of bloody serum in the 

 abdomen. 



Not a trace of iron or potash were found in this serum or 

 in any of the tissues. 



No Prussian blue in the thoracic duct or elsewhere. 



Experiment 4. — Injected one and a-half ounce of warm 

 saturated solution of ferrocyanide of potassium beneath the 

 skin of the back of a large clog. Some hours after urine was 

 voided, containing abundance of the salt injected. This upon 

 evaporation yielded yellow crystals. No trace of blue. 



Experiment 5. — Saturated some hiunan urine with ferro- 

 cyanide of potassium. On evaporation ciystals, as in the last 

 experiment. No blue colour. 



It thus appears that when iron is introduced into the system, 

 it passes ofi" by the kidneys in combination with some 

 other constituent, from which it is only separated by heat, 

 when, if the ferrocyanide of potassimn is present, prussian 

 blue is immediately formed. It does not appear that the 

 feiTocyanide of potassium is in any other state than solution. 

 Neither of the salts were ever detected in the feeces ; the 

 same is true of the aniline dyes. 



It is known that ferrocyanide of potassimn, by exposure, 

 assumes a blue tint, yet is still crystalline. Experiments 4 

 and 5 were instituted to see if, by the process of evaporation, 

 a similar colour could be produced, so as to cause a doubtftil 

 result. They prove clearly the presence in Experiments 1, 

 2, and 8, of a far larger amount of iron than is contained in 

 any ferrocyanide, sufficient indeed to produce the well- 

 known amorphous prussian blue of commerce. 



Whilst these experiments show no such combination takes 

 place within the body, still they reveal the presence of a salt 

 in the blood, chyle, and urine, which upon evaporation at 

 ordinary temperatures appears as minute bright blue 

 crystals. 



