196 
DR. L. WALDSTEIN. 
alkaline reaction was shewn with rosolic acid, whereas litmus 
paper was not changed. 
It is clear, therefore, that at the temperature of the incubator 
and of the water bath urea is decomposed in a comparatively 
short space of time, and that the presence of the alkali serves to 
facilitate it. The slowness of the generation of ammonia in 
tube IV is of especial interest when brought in relation with 
the contents of the retorts of the first series. Here, also, when 
other tests for free ammonia are not available, a little of the 
solution of rosolic acid on a cotton plug, held over the mouth 
of the vessel, is a delicate reagent; care must naturally be 
taken that the plug does not touch the tube, nor that it be 
exposed to the air too long, for the smallest traces of atmospheric 
ammonia will show the colour reaction. 
With reference to the change of the reaction, attention ought to 
be called to one retort, mentioned above, which contained or- 
ganisms, and, notwithstanding, showed acid reaction. This 
retort was charged, July 11th, with urine of the acidity of eighty 
drops, together with a liq. pot. tube, which remained intact. On 
October 17th it was opened and examined, when the acidity was 
found to be reduced to thirty-five drops of 5*85 percent, liq. pot. 
Dr. Bastian has already called attention to the reduction of the 
degree of acidity under similar conditions. 
Notwithstanding the minute description which Dr. Bastian has 
given of his method it is, as in all cases of experimentation with 
fluids of unknown or inconstant composition, never possible to 
repeat the tests and draw the same conclusions. The simpler the 
pabulum, and the more we have it in our power to modify its 
composition, the more uniform will be the results of cultivations 
of organisms. I have, therefore, sought to study the question, 
making use of Mayer^s solution,^ modifying it in such a manner 
that, instead of adding tartrate of ammonia, I introduced urea 
(1*06 grm. to 30 c. c.), after the solution of the other salts 
had been boiled and filtered. After dissolving the urea the solu- 
tion was again filtered. Although Cohn has found that this is 
not a very good pabulum, I would, in reference to my results, 
call attention to the fact that he himself has seen Bacteria 
develop and multiply in a simple solution of the milk sugar 
of commerce, and that he believes that the nitrogen was absorbed 
from the surrounding atmosphere. With this solution a number 
of test tubes were charged, sealed, and placed in the incubator 
122° 1\ (40 — 45° C.). After sixty-five days all specimens were 
turbid and swarmed with organisms ; the degree of acidity of 
30 c. c. was reduced from 110 drops to 66 drops. It seemed 
1 •! grm. of potassium phosphate, ’1 grm. crystallised magnesium sul- 
phate, *01 grm. tribasic calcium phosphate to 100 c. c. distilled water. 
