A CONTRIBUTION TO THE BIOLOGY OF BACTERIA. 193 
The fresh filtered urine wliich I used never showed precipita- 
tion of phosphates or albumen on boiling, and in order to 
ascertain the degree of acidity a previously boiled specimen of it 
was tested. This latter precaution, and the addition of the two- 
thirds proportion of liq. pot., was only adopted, however, after 
the result was found to be other than that recorded by Mr. 
Bastian, with urine whose degree of acidity had been determined 
with portions previously unboiled and mixed in the prepared 
retorts with liquor potassse of the proportion of three-fourths of 
its acidity. To facilitate the determination of the degree of 
acidity a burette was constructed, with a capillary termination 
by means of which drops of known weight (0*0075 grms.) of 
the liquor potassse could be mixed gradually with 30 c. c. of 
urine. The equality of the drops was insured by suitable pre- 
cautions, the liq. pot. changed and the instrument well cleaned 
from time to time. In the first series of experiments litmus 
paper was used, but ever after rosolic acid, a very delicate re- 
agent. In determining whether or not the contents of the 
retorts contained organisms, three to five specimens from every 
vessel were examined, and only then was their presence noted 
when they could either be distinguished by their characteristic 
movements or other signs of life, such as, for instance, an 
increase in the size of the zoogloea masses, and when caustic, 
liq. potassge, and strong acetic acid failed to dissolve the sus- 
pected bodies. In all more than fifty retorts were charged and 
examined. 
The fluids, which were mixed with the proportionate amount 
of liq. pot., and which were examined at intervals between 
twenty-four to seventy -two hours and fourteen days, were all 
found turbid and showed sedimentation, but not one of them 
contained organisms; the sediment was, moreover, found to 
consist of phosphates, crystalline, and amorphous masses on 
being examined by means of micro-chemical tests. Their odour 
was not appreciably changed, not even in those specimens which 
contained triple phosphate crystals. 
This result remained the same after using urine from other 
individuals, and after adding peptone to some specimens. In 
order to make quite sure that organisms were not contained in 
the fluid, at least wdthin the limits of all means of examination, 
portions of the same were allowed to form sediment in narrow glass 
tubes with a capillary termination, and the first drops carefully 
searched through under the microscope. In all these trials the 
result remained the same. 
After remaining in the incubator during one month the 
specimens containing unbroken liquor potasssc tubes were found 
clear with very few exceptions, and, when examined, contained 
