

DISCUSSION WITH M. PASTEUR 153 
They began by providing liquor potassz sufficient 
for accurately neutralising the quantity of urine em- 
ployed (instead of three-fourths, of that amount, as I 
advised) ; they boiled the urine over the flame for five 
(rather than for one or two) minutes, a procedure which 
was found by Pasteur, as well as by myself, to lead toa 
decomposition of urea into ammonium carbonate ; 
and then the closed flasks were kept for fourteen 
days ina “ warm place,” during which time, as I have 
fully shown elsewhere, a still further reduction in the 
acidity of the urine would go on, though more slowly. 
The combined effect of providing too much potash 
in the first place, of diminishing the acidity of the 
urine by the more prolonged heating over the flame, 
and still further by keeping it in a warm place for a 
fortnight before the liquor potassze was liberated 
from the little tubes, was such as inevitably to lead 
to the cause of failure to which I had specially called 
attention. Though probably neither of these 
experimenters knew about the lowering of the 
acidity of the urine by the boiling and during its 
subsequent stay in the warm place, full details on 
this subject are to be found in my memoir in the 
Journal of the Linnean Society (Zool.), vol. xiv. pp. 
28-43, which was published in the following year— 
some extracts from which on this subject are to be 
found in the next chapter (pp. 170-173). 
- a — 
Having shown the reason why Sir William 
Roberts and Professor Tyndall failed in their 
attempts to repeat my experiments, we may now 
turn to what M. Pasteur had to say concerning them. 
