1866.] resembling Quinine, in Animals , ^c. 77 



Among all the delicate tests for different organic substances, the fluo- 

 rescence of sulphate of quinine appeared likely to afford good results ; for 

 the following experiments on the delicacy of this test for sulphate of quinine 

 show that this method of tracing sulphate of quinine into and out of the 

 body, though inferior to the spectrum determinations of lithium, was supe- 

 rior in delicacy to the spectrum determinations of many other substances. 



0}i the Delicacy of the Fluorescent Test of Sulphate of Quinine when a 

 Ruhmkorf coil was used as the source of light. 

 One grain of sulphate of quinine was dissolved in five ounces of acidified 

 water, and this was again and again diluted until one grain of quinine- salt 

 was present in 1,800,000 parts of water. This, when examined in a quartz 

 cell by the induction-spark, showed blue fluorescence distinctly in twenty 

 grains of solution. 



Another grain, dissolved in a litre and diluted until one grain of salt was 

 present in 1,440,000 parts of water, when acidified, also showed the fluo- 

 rescence distinctly in twenty grains of solution. 



The same quantity, dissolved in one litre of water, was diluted to 512 

 litres. This was equal to one part in 7,200,000 parts of water; as the 

 fluorescence could be seen in twenty grains of this solution, gg^^ of a 

 grain of sulphate of quinine gives the fluorescence. 



In another experiment, of sulphate of quinine, in fifty minims of 

 water acidified, showed the fluorescence strongly, and even Y^^om ^ 

 grain of sulphate of quinine in fifty minims of water showed the fluores- 

 cence feebly. As the fluorescence could be seen in twenty grains of this 

 solution, -—-^ of a grain of sulphate of quinine gives the fluorescence. 



In the last two sets of experiments the light of a bright induction-spark 

 was concentrated by a small quartz lens. 



One grain of disulphate of quinine, dissolved in 256 litres of water acidu- 

 lated with one-eighth of sulphuric acid (1 to 8), shows fluorescence feebly in 

 a quartz cell containing twelve grains of the solution. Hence grain 

 gives the fluorescence feebly. 



If one grain of disulphate of quinine is dissolved in a thousand litres, or 

 one part of quinine to 15,440,000 of water, the fluorescence is still percep- 

 tible in one ounce of the solution. 



On the Existence of an extr actable Fluorescent Substance in Animals 



and Man. 



Immediately on trying to apply this reaction to test the different tex- 

 tures of guineapigs, after and before they had taken quinine, we found that 

 in health no part of any of the tissues of the guineapig was free from blue 

 fluorescence. It became desirable, therefore, to separate the fluorescence 

 produced by some fluorescing substance normally present in the tissues 

 from that produced after quinine was given. After very many attempts 

 to extract these substances separately from the tissues, and many more to 

 separate them when they were conjointly extracted, all of which proved 



