318 Mr. C. Russ. [May 21 ; 



43 substances (a list of which is appended) tried in this way, a decided 

 aggregation was observed with ethylamine, ammonium sulphate, aeetamide, 

 and iodide of potash. The first three will be noticed to contain an NH 2 or 

 NH 4 group. The aggregation in aeetamide or potassium iodide is anodic, but 

 weaker than the cathodic aggregation in ethylamine, or ammonium sulphate. 



A curious effect was noticed with ammonium sulphate, viz., an early 

 aggregation at the cathode, soon followed by a sinking away of the massed 

 organisms, resulting in the appearance of a clear zone between the bacterial 

 cloud and the platinum foil. This was probably the result of some 

 secondary electrolysis at the terminal in question ; this disturbing action led 

 to the abandonment of ammonium sulphate for the purposes of these 

 experiments. 



A good accumulation was found to occur with a mixture of ethylamine and 

 lactic acid, the migration of the bacilli being towards the cathode ; separate 

 tests indicated no reaction in lactic acid, and a moderate one with ethyl- 

 amine alone. The movement of the tubercle bacillus in normal urine was 

 found to be slightly anodic. The addition of urine to the lactic acid and 

 ethylamine did not interfere with the aggregation of the tubercle bacilli at 

 the cathode. At the end of the test the presence of the bacilli in large 

 numbers at the cathode, and their absence at the anode, was confirmed by 

 making stained films from the cloudy and clear fluids round the respective 

 poles. 



It was, however, noticed in these films that the bacilli stained feebly after 

 several hours of electrolysis in the ethylamine lactic acid and urine mixture ; 

 this difficulty was overcome by the addition of bromic acid to the mixture. 



The proportions of these substances found to be most satisfactory were : — 



Ethylamine, 5-per-cent. solution One part. 



Lactic acid, 10 „ Four parts. 



Bromic acid, 5 „ Two parts. 



Urine One or two parts. 



It may be useful to mention here that when electrolytes are added to 

 urine, and the mixture electrolysed, there is formed at the cathode a white 

 flocculent substance which is insoluble in the fluid, but soluble in mineral 

 and organic acids. As this substance is easily mistaken (in aggregation tests 

 in urine) for the bacterial cloud expected at the electrode, the solubility in 

 acid should be tested for. It may further be distinguished by its rapidity of 

 appearance and buikiness of the cloud, in which particulars it contrasts with 

 the true bacterial massing at the foil ; the lactic acid used in the mixture 

 above mentioned prevents its formation. 



