Insect Colouring 



operate on a larger scale. The adipose tis- 

 sue taken from a number of larvae is treated 

 with nitric acid. The effervescence is as 

 lively as if the reaction were taking effect on 

 a bit of chalk. When it has subsided, some 

 yellow clots are floating on the surface. 

 These are easily separated. They come 

 from the fatty substance and the cellular 

 membranes. There remains a clear liquid 

 containing the white granules in solution. 



The riddle of these granules was being 

 presented to me for the first time; my pre- 

 decessors had provided no physiological or 

 anatomical data to guide me; great there- 

 fore was my joy when, after a little fum- 

 bling, I succeeded in hitting upon their char- 

 acteristic feature. 



The solution is evaporated in a small 

 porcelain capsule, placed on the hot embers. 

 On the residue I pour a few drops of am- 

 monia, or else simply water. A glorious 

 crimson colour at once makes its appearance. 

 The problem is solved: the colouring-matter 

 which has just formed is murexide ; and con- 

 sequently the powdery substance which filled 

 the cells was none other than uric acid, or 

 more precisely ammonium urate. 



A physiological fact of this importance can 

 hardly stand alone. Indeed, since this basic 

 277 



