172 On Absorption. 



In other experiments he substituted for the galls a solution 

 of ferrocyanide of potassium, and succeeded in discovering 

 Prussian blue in the thoracic duct and elsewhere. 



Again, one of ohr best workers in science, Mr. Ralph, of 

 Kew, near Melbourne, in a paper read before the Medical 

 Society of Victoria, December 6th, I860, states, that when 

 prussic acid has been either swallowed or inhaled, minute 

 particles or films of prussian blue, may, with the aid of the 

 microscope, be detected in the blood ; and along with these, in 

 very many instances, he has observed bodies resembling 

 starch-grains, which polarize, and upon the addition of iodine 

 turn purple. His theory is, " that the prussic acid is more 

 or less nutralized in the blood by the iron present in it, and 

 in proportion to the iron thus withdrawn, there is so much 

 starchy matter set free." 



My own results are as follows : 



Experiment 1. — At 11, a.m., March 28th, 1866, I injected 

 asolution of ferrocyanide of potassium into the peritoneal cavity, 

 and a solution of perchloride of iron beneath the skin of 

 the back of a fowl. 



Purging and passing of urine soon followed. On testing 

 the urine for iron, none was discovered, but abundance of the 

 ferrocyanide of potassium. The tests used were — for the iron, 

 tincture of galls and ferrocyanide ; for the ferrocyanide, 

 perchloride of iron. No amorphous prussian blue was found 

 in the blood, but on evaporation numbers of minute crystals 

 were observed with the microscope, some green, many 

 *' darkly, deeply, beautifully blue, as some one somewhere 

 sings about the skies." As there are both yellow and blue 

 ferrocyanide of potassium, it was impossible at this stage of 

 the experiment to speak with certainty as to the presence of 

 prussian blue in the blood. 



At half-past 12, p.m., made the bird swallow four ounces of 

 the solution of perchloride — seemed to like it. Urine and 

 blood aggtin examined — ^result as before. 



At 9 o'clock, the following morning, the urine gave no 

 trace of either iron or ferrocyanide of potassium, and the bird 

 was quite well. It was now killed. 



The contents of the thoracic duct were to the naked eye 

 colourless — no appearance of prussian blue — no evidence 

 either of iron or ferrocyanide upon using the ordinary tests. 

 A drop drying on the microscope yielded the same undeter- 

 mined crystals as the blood. 



Upon touching any part of the peritoneal cavity with a 



