1876.] 



Liquor Potassce ^c. on Microphytes. 



455 



that in adding the liquor potasssD due care is taken that no new germs are 

 introduced at the same time. In repeating my experiment, Dr. Bastiaii 

 appears to have departed from my procedure in two points, and he has 

 til us possibly laid himself open to the two sources of fallacy just 

 mentioned. In my own experiments, the acid infusion, after it had been 

 boiled, was set aside in a warm place for a fortnight in order to test its 

 sterility ; and the liquor potasse was not added to it until the lapse of 

 time had satisfied me that it had been rendered permanently barren. In 

 Dr. Bastian's experiments the liquor potassse was added as soon as the 

 vessels had cooled, so that he had no certainty that their contents would 

 not have germinated without the addition of the alkali *, In the second 

 place, instead of heating the tubes containing the liquor potassse (as I'had 

 done) to 250° T., and thus ensuring the destruction of all germs contained 

 in the air imprisoned therein with the alkali, he contented himself with 

 subjecting them for an inconsiderable period to the heat of boiling water. 



Seeing these two possible sources of fallacy, I determined to repeat Dr. 

 Bastian's experiments with urine, but taking care to avoid these 

 defects. I proceeded as follows : — 



A flask with a longish neck was charged with an ounce of normal acid 

 urine. The due quantity of liquor potassae requisite to exactly neutralize 

 this (as ascertained by previous trials) was enclosed in a sealed glass 

 tube drawn to a capillary portion at one end. The tube was then heated 

 in oil up to 280° T., and maintained at that temperature for fifteen 

 minutes. The tube was then introduced into the body of the flask. The 

 neck of the flask was next drawn to a narrow orifice ; then the urine 

 was boiled for five minutes, and the orifice sealed in ebullition. Ten 

 such flasks were charged and treated in the same manner. They were 

 then set aside in a warm place (from 70° F. to 80° T.) for a fortnight. 

 At the end of this time the contents of the flasks were found perfectly 

 transparent ; the urine was therefore assumed to be permanently steri- 

 lized. The liquor potassaD was then liberated by shaking the tubes 

 against the sides of the flasks, and thus breaking their capillary points. 

 The previously acid and barren urine was thus neutralized. The flasks 

 were then placed in an incubator, and maintained at a constant tempera- 

 ture of 115° r. At the end of two days it was found that the urine in 

 each flask had deposited a sediment of earthy phosphates ; but the super- 

 natant liquid was perfectly transparent. The flasks were again placed 

 in the incubator, and maintained at a constant temperature of 122° F. 

 for three days. At the end of this period they were withdrawn and 

 opened for examination. Not one of them showed the slightest evidence 

 of living organisms ; the supernatant liquid was perfectly transparent, 

 and no Microphytes could be detected under the microscope. The pre- 



* It is not sufScient to rely in such a case on a control flask or retort. Each flask 

 or retort should have its own individual sterility tested, because it is practically im- 

 possible to apply the heat exactly in the same degree in any two cases. 



