On Kreatinins. 



493 



dride), continuous currents of very considerable power may be 

 obtained when the internal resistance is diminished sufficiently by 

 nsing cells of considerable magnitude ; e.g., when made of the stone- 

 ware and inner porous vessels usually employed for Grove's cells, the 

 porous vessel being cemented into the outer stoneware vessel (by 

 paraffin wax or other unattacked material) in such a fashion as to 

 divide it into three compartments separated one from the other by 

 porous dividing walls ; the acid and alkaline fluids being placed in 

 the two outermost compartments, and the innermost one being filled 

 with a solution of a neutral salt, e.g., sodium sulphate. A large 

 variety of analogous cells of more or less power can thus be formed by 

 using different organic and inorganic reducing substances soluble in 

 alkali, e.g., ferrocyanides, hydrosulphites, opianates, &c. 



"On Kreatinins. I. On the Kreatinin of Urine as distin- 

 guished from that obtained from Flesh Kreatin, II. On 

 the Kreatinins derived from the Dehydration of Urinary 

 Kreatin." By George Stillingfleet Johnson, M.R.C.S., 

 F.C.S., F.I.C. Received May 5,— Read June 10, 1887. 



Part I. 



I was induced to undertake this investigation by a careful observa- 

 tion of the action of picric acid and potassium hydrate upon normal 

 human urine at the boiling temperature. 



The introduction of picric acid as a test for sugar in urine is due 

 to my father, Dr. George Johnson, who accidentally discovered the 

 production of a very dark colour on the addition of picric acid to a 

 portion of saccharine urine which had been previously boiled with 

 potassium hydrate. He made this observation in November, 1882. 

 The dark colour was found to be due to reduction of potassium 

 picrate to potassium picramate by glucose at the boiling temperature, 

 and in presence of potassium hydrate. The reaction had been 

 described by C. D. Braun nearly twenty years previously ("Ueber 

 die Umwandlung der Pikrinsaure in Pikraminsaure und iiber die 

 Nachweisung des Traubenzuckers," ' Fresenius, Zeitschrift,' 1865), 

 but it had not hitherto been applied to any practical purpose. 



Having observed the extreme delicacy of the test, and the ease with 

 which the reaction is effected, my father determined to introduce it to 

 the notice of the medical profession, not merely as a trustworthy 

 qualitative test of extreme delicacy, but also as a means of estimating 

 quantitatively the actual amount of glucose in diabetic urines. In 

 this latter object I did my best to assist him, and our united efforts 

 resulted in the elaboration of a new, easy, and accurate method for 



