July 6, 1876] 



NATURE 



221 



Previous experimenters have never designedly had recourse to 

 a generating or developing temperature above 100° F, (38° C). 

 The heat employed has frequently been below 77° F. (25° C), 

 though a temperature between this and 95° F. (35° C.) has been 

 regarded both by chemists and biologists as most favourable to 

 the occurrence and progress of fermentative changes generally. 



Early in the month of August, 1875, the author ascertained the 

 fact that some boiled fluids which remained barren when kept at 

 a temperature of 77°-86° F, (25°-30° C.) would rapidly become 

 turbid and swarm with organisms if maintained at a temperature 

 of 115° F. (46° C). More recently he has discovered the sur- 

 prising fact that a generating temperature as high as 122° F. 

 (50° C. ) may be had recourse to with advantage in dealing with 

 some fermentable solutions. Fluids which would otherwise have 

 remained barren and free from all signs of fermentation have, 

 under the influence of this high temperature, rapidly become 

 turbid and corrupt. This discovery is regarded as of great im- 

 portance in reference to the questions now under discussion, and 

 it is one which was quite unexpected. The author had pre- 

 viously shared in the generally received opinion that tempera- 

 tures above 100° F. (38° C.) were likely to impede rather than 

 promote fermentation. 



In maintaining the experimental fluids at the high temperature 

 above-named, the vessels containing them were placed in the 

 hot-air chamber of an incubator, such as physiologists employ, 

 to which one of the very ingenious gas- regulators of Mr. F. S. 

 Page had been fitted (see Journal of the Chemical Society, 

 January, 1876). In this way the fluids may be kept at a known 

 and practically constant temperature for an indefinite time. 



Liquor Potassa as a Promoter of Fermentation in Boiled Urine. 



In the autumn of 1875 the author instituted some experiments 

 to ascertain whether the fermentability of boiled urine, like that 

 of many other fluids, could be increased by previously mixing 

 with it a quantity of liquor potassae sufficient for its neutraliza- 

 tion. 



The experiments answered this question in the aifirmative. It 

 was found that urine to which the above-named amount of liquor 

 potassse had been added, would constantly ferment and swarm 

 with organisms vnthin a few days after it had been boiled ; 

 though some of the same stock of urine in the acid state (that is, 

 without the addition of any alkali) would when similarly treated 

 in other respects, remain barren. The fact of the production of 

 an increased fermentability in boiled urine by previous neutralisa- 

 tion was thus established. 



Further experiments were then instituted to throw light upon 

 the cause of such increased fermentability. It was desirable to 

 ascertain whether (i) it was due to survival of germs in the boiled 

 neutralised fluid, or (2) to the chemical influence of potash in 

 initiating or helping to initiate the molecular changes leading to 

 fermentation in a fluid devoid of germs or other living matter. 



The mode of testing the relative validity of these rival inter- 

 pretations seemed easy. It was only necessary to ascertain what 

 the effect would be of adding boiled liquor potassse, in proper 

 quantity, after the acid urine had been rendered barren by boiling 

 it instead of adding it previous to the process of ebullition. If 

 fermentation occurred in the fluid thus neutralised without ex- 

 traneous contamination, the first interpretation would obviously 

 be negatived. 



This crucial experiment was at first tried with flasks plugged 

 with cotton-wool, the plug in each of them being penetrated by 

 a closed glass tut)e containing the measured amount of liquor 

 potassse. The tubes having been drawn out to a capillary por- 

 tion at the lower end, and bent at an obtuse angle, they could be 

 easily broken by slight downward pressure against the bottom of 

 the flask whenever it was desired to mix the liquor potassse with 

 the boiled urine. This apparatus was very similar to that first 

 made use of by Dr. William Roberts in some experiments with 

 hay-infusion (Phil. Trans, vol. clxiv. p. 474), in which he ob- 

 tained opposite results from those now about to be recorded 

 with urine. The latter fluid is, however, for several reasons 

 more suitable than hay-infusion for trying such experiments. 



Several trials made with urine in this apparatus showed that 

 its fermentability was just as much increased by adding boiled 

 liquor potassse after the urine had been boiled in the acid state, 

 as by adding the alkali previous to the process of ebullition. 

 Such a result was therefore quite opposed to the first interpreta- 

 tion as to the cause of the increased fermentability of neutralised 

 urine. 



The definite overthrow or establishment of this interpretation 

 was so important that it seemed desirable to try such experi. 



ments again by some more rigid and certain method. The 

 author, therefore, devised a new mode of experimentation in 

 which sealed retorts replaced the flasks plugged with cotton- 

 wool, and in which the contents of the enclosed liquor-potassse 

 tubes could be more efTectually heated. 



It was first of all ascertained that accurately-neutralised urine 

 boiled in a retort and sealed whilst boiling, would ferment in a 

 day or two if kept at a temperature of 122° F. 1 



This fact having been established, other retorts were charged 

 with a measured amount of urine, and also with a small glass 

 tube containing liquor potassse in quantity almost sufficient to 

 neutralise the urine employed. 2 The glass tubes containing the 

 liquor potassse had been drawn out at one end, sealed, and then 

 immersed in boiling water for different periods before introducing 

 them into the retovts. After each retort had been charged with 

 urine and a liquor potassse tube, its neck was drawn out to a 

 capillary point, the urine was boiled, and the retort was her- 

 metically sealed before ebullition had ceased. Thus closed, the 

 vessel was at once immersed with its neck downwards in a can 

 of boiling water for from four to fifteen minutes, so as to expose 

 it and its contents for an additional period to a temperature of 

 212° F. (100° C). 



The urine was thus boiled in, its unaltered acid state and 

 sterilised. After the retorts had cooled the liquor potassse was 

 liberated from its tube in all but one of the batch, which was 

 kept as a control experiment. The liberation was easily effected. 

 It was only necessary to give the retort a sudden shake so as to 

 drive the capillary neck of the enclosed tube against its side. 

 The tube was thus broken and immediately (owing to the com- 

 parative vacuum within the retort) the liquor potassse was sucked 

 out and mixed with the fluid which it was destined to neutralise. 



The result of these experiments was similar to those executed 

 with the plugged flasks and liquor-potasste tubes. The boiled 

 caustic potaf^i added afterwards within the sealed retorts, caused 

 the previou::!/ barren fluids to ferment and swarm with Bacteria. 

 The fluid in the control experiment remained pure, though after 

 several days, or longer, it also could be made to ferment by 

 breaking the liquor-potassse tube, and replacing the retort in the 

 warm chamber. 



Effects of liberating Oxygen by Electrolysis within the Close i 

 Retorts. — A few other experiments were made with retorts to 

 which platinum electrodes had been fitted. These contained, as 

 before, measured amounts of urine, together with liquor potassa; 

 tubes. All the preliminary'stages were similar to those of the 

 experiments above recorded; but just before breaking the 

 liquor-potassse tubes in these further experiments, oxygen and 

 hydrogen were liberated from the boiled urine by electrolysis. 



The result in the few experiments made was very remarkable. 

 Under the combined influence of liquor potassse, oxygen, and 

 the high temperature of 122° F. (50° C), the sterilised urine 

 fermented and swarmed with Bacteria within the closed retorts 

 in from 7-12 hours — that is, in a much shorter time than would 

 suffice for the occurrence of similar changes in unboiled urine 

 freely exposed to the air. 



Behaviour of some specimens of unaltered Acid Urine under the 

 influence of the High Generating Temperature of 122° F, 

 (50° C). 



In the course of the previous experiments it was found that 

 occasionally a specimen of boiled urine would ferment at a tem- 

 perature of 122* F. without the addition of liquor potassse. This 

 was afterwards ascertained to occur invariably (with the urine 

 experimented upon) when the acidity of the fluid was not higher 

 than would be represented by six minims of liquor potassse to 

 the ounce (or about i^ per cent.). Urines slightly more acid 

 than this sometimes did and sometimes did not ferment without 

 liquor potassse ; but when the acidity exceeded what would be 

 equivalent to two per cent, of liquor potassse, the fluid did not 

 ferment under the influence of the high generating temperature 

 alone. Urines of all degrees of acidity, however, were found to 

 ferment under the combined influence of heat and liquor potassse 

 added afterwards, in the manner already detailed,^ 



* Though the boiled urine will ferment in retorts from which the air has 

 been expelled by boiling, it will undergo this change more quickly if it is in 

 the presence of purified or sterilised air. lu the experiments now about to 

 be described, however, it was much more convenient to use airless retorts. 



2 As a slight excess in the amount of liquor potassae has been proved to 

 have a most restrictive influence when dealing with urine, it was found safer 

 in these experiments not to provide liquor potassa; sufficient for full neutrali- 

 zation. Many details on this subject are given in the memoir itself. 



3 In the uiine of highest acidity with which experiment has been made, 

 twenty minims of licjuor potassx to the fluid ounce (about 4 per cent.) was 

 required for neutralisation. 



