494 



Mr. G. S. Johnson. 



determining sugar in urine, which is fully described in Dr. G. John- 

 son's volume of ' Medical Lectures and Essays,' and also in the last 

 edition of Dr. Roberts' work on ' Urinary and Renal Diseases.' 



Reaction of the Picric Acid and Potash Test in Normal Human Urine. 



As soon as the picric acid and potash test was introduced to my 

 notice, I applied it to normal human urine, and found that it gave 

 indication of the presence therein, if not of glucose, at all events of 

 a reducing substance capable of reducing yellow potassium picrate to 

 red potassium picramate in presence of potassium hydrate at the 

 boiling temperature. 



After the elaboration of the test as a quantitative one, many speci- 

 mens of urine from men in perfect health were examined by its means, 

 and we never met with a single specimen which gave no reducing 

 action, though, as would be expected, the reduction was more marked 

 in concentrated specimens, and the smallest quantity of reducing sub- 

 stance was found in the urine of patients suffering from diabetes 

 insipidus, in which cases the specific gravity of the secretion was very 

 low. 



In most urines from healthy individuals, of the average specific 

 gravity (1*020), the amount of reduction exerted upon picric acid in 

 presence of potassium hydrate at the boiling temperature corresponded 

 with that which would have been produced by a solution of glucose 

 containing 0'6 grain per fluid ounce ; whilst the quantity of reducing 

 agent indicated by the method of Fehling or Pavy is always slightly 

 greater, the cupric oxide reduction of normal human urine expressed 

 in terms of glucose averaging 0'75 grain per fluid ounce. 



But is this normal reducing agent glucose ? and if not, what is it ? 

 The object of the present research is to answer these questions. 



Observations which negative the Hypothesis that the Reducing Agent of 

 Normal Urine is Glucose. 



Dr. Robert Kirk (' Lancet,' June 16, 1883) was, I believe, the first 

 to publish the fact that healthy urine gives some indication of reducing 

 picric acid in presence of potash at the ordinary temperature, whereas 

 glucose effects no redaction until the temperature approaches the 

 boiling point. This is an important distinction. 



Again, after repeated experiments, I have never once succeeded in 

 producing alcohol and carbon dioxide from normal human urine by 

 the action of yeast, even when the solution was artificially concen- 

 trated before introducing the yeast, and the liquid containing the 

 ferment was kept under the most favourable conditions of tempera- 

 ture, &c. 



