78 



Messrs. Jones and Dupre on a Substance, [Apr. 12, 



unsuccessful, we resorted to the plan of determining the amount of natural 

 fluorescence by comparing it with standard solutions of sulphate of quinine ; 

 and by the same means we measured the increase that occurred in the 

 amount of fluorescence from the same organs after quinine had been taken. 



The following plan was adopted for the extraction of the fluorescent sub- 

 stance from the textures, both before and after quinine was taken. 



The part to be examined was treated on a water-bath with very dilute 

 sulphuric acid, either directly or after previous drying in a water- oven. 

 This extraction was repeated again and again. The acid extracts were 

 mixed, filtered after cooling, neutralized with caustic soda, and repeatedly 

 shaken up with their own bulk of ether. The residue left after evapora- 

 tion of the ether was taken up by dilute sulphuric acid, filtered, and 

 tested for the amount of fluorescence after having been made up to a cer- 

 tain bulk, generally twenty-five minims. 



When a large quantity of material, as two or three pounds of liver, was 

 employed, the acid extract was a second time neutrahzed and treated with 

 ether ; the residue from the second ethereal solution was then taken up 

 with dilute sulphuric acid and tested. 



In very dilute solutions the fluorescence of the animal substance cannot 

 be distinguished from that produced by quinine ; if the solution is more 

 concentrated, the fluorescence of the animal substance is confined much 

 more to the surface, the fluorescence in a solution of quinine passing much 

 further into the liquid ; and in still more concentrated solutions, the colour 

 of the light given out is of a decidedly greenish hue. The fluorescence 

 also of the animal substance begins to appear somewhat nearer to the red 

 end of the spectrum than is the case with quinine ; but both extend to the 

 same distance beyond the violet end. 



From two to three pounds of liver, only about fifty minims of a solution 

 was obtained showing a fluorescence equal to that produced by two or 

 three grains of quinine to the litre of water ; and when slightly acidified, 

 the following reactions were obtained with the solution. It gives a preci- 

 pitate with solution of iodine, with a solution of iodide of mercury in iodide 

 of potassium, and also with phosphomolybdic acid, bichloride of platinum, 

 and terchloride of gold : this last precipitate is soluble in alcohol, Hke that 

 produced in solutions of quinine. 



A weak solution of quinine interposed in a quartz cell before the solu- 

 tion of the natural fluorescing substance, did not stop the fluorescence of 

 this latter substance entirely ; but when the solution of animal substance 

 was placed before the solution of quinine, no fluorescence whatever could 

 be perceived in the quinine. Ether is unable to extract the animal sub- 

 stance from an acid solution ; the acid solution may be shaken up several 

 times with ether ; but the ethereal solution on evaporation yields a residue 

 which, when taken up by dilute sulphuric acid, gives no blue fluorescence 

 whatever. 



The fluorescence of this animal substance is much less strong in hydro- 

 chloric acid solutions by the light of the coil-spark, and it is almost destroyed 



