— 137 — 
In order to ascertain in what form piperonal is excreted from the body 
of the frog, the urine of several frogs which had received a piperonal-injection, 
was collected. This urine, which had no aromatic odour, was slowly evapo- 
rated almost to dryness; after acidifying with hydrochloric acid it was ex- 
tracted with alcohol, and the alcohol driven off. There remained as a residue 
small crystalls which were insoluble in cold water, but readily dissolved in 
alcohol and ether. These properties, and also the melting point and the 
capacity of subliming, proved that it was a question of piperonylic acid. The 
melting point no doubt lay at 223°, that is 4° lower than that of pure 
piperonylic acid. But this small error is of no further importance, as already 
slight contaminations reduce the melting point by many degrees. The remainder 
of the piperonylic acid was once more purified by subliming, but the quantity 
was too small for the determination of the melting point. 
It follows that, as in the organism of the rabbit and the 
dog, piperonal in the body of the frog is converted into the 
allied piperonylic acid; it can be identified as such by its 
capacity of subliming, and by the determination of the 
melting point. Piperonyluric acid is not present in the urine 
of the frog. 
