CONDITIONS FATOURING FERMENTATION. 



25 



iu other companion retorts whose contents were similar, except 

 for the fact tliat they contained no atmospheric air. The libera- 

 tion of the liquor potassj© from the tube with a capillary neck 

 can only be brought about with great difficulty in a retort con- 

 taining air ; and this was the reason of my giving up the condi- 

 tions more favourable to the fermentation of the boiled urine, iu 

 order to avail myself of the facile and automatic emptying of the 

 liquor-potassse tube which takes place in the retort from which air 

 has been expelled by boiling. 



In a trial of the combined effects of oxygen and alkali upon 

 urine whose specific gravity was 1028, and whose acidity was neu- 

 tralized by 18 minims of liquor potassse to the ounce, distinct tur- 

 bidity of the fluid of the retort to which oxygen had been added 

 made its appearance in thirteen hours ; whilst in a companion 

 vessel similarly treated, except for the absence of free oxygen and 

 hydrogen, turbidity did not show itself till the expiration of the 

 forty-first hour. 



On another occasion, when experimenting with urine w^hose 

 specific gravity was 1023 and whose acidity was neutralized by 

 5 minims of liquor potassse to the ounce, I found that the fluid in 

 two retorts into which liquor potassse had been liberated, and also 

 a quantity of oxygen and hydrogen, became distinctly turbid in 

 five and seven hours respectively ; whilst the fluids in companion 

 vessels similarly treated, except for the absence of oxygen and 

 hydrogen, did not show signs of turbidity before 22 1 hours. 

 This result was very remarkable, since, under the combined influ- 

 ence of liquor potassse, oxygen, and a temperature of 122° F., a 

 specimen of boiled urine became turbid much more rapidly than 

 a simple specimen of unboiled urine would have done, exposed to 

 a temperature of 77°-86° F. 



It seems quite useless for me, in the present state of inquiry in 

 regard to these questions, to dwell upon the fact of the number of 

 times I have produced this or other results, or to describe them in 

 more detail. What I seek to do now is, by careful description of 

 my methods, to enable others, who will exercise proper care, to 

 obtain similar results. With this object in view, I shall, in the 

 first place, refer to certain causes of failure, and to certain causes 

 of variation in the time of supervention of fertility in sterilized 

 urine under the influence of liquor potassse, to which I have already 

 drawn attention in a previous paper*, in order to show why 

 * Now deposited in the Arcliires of the Eoyal Society. 



