168 THE EVOLUTION OF LIFE 
amount of potash, when, at last, they broke their 
potash tubes. 
We now have to turn to Pasteur’s method of 
repeating this experiment, and must try to ascertain 
why he also failed to obtain my results. The actual 
cause for some little time proved to be a great 
puzzle to me, though from the first, as will have 
been seen from the discussion between us, as 
recorded in the last chapter, I conjectured that 
his uniformly negative results must have been due, 
as with the experimenters above referred to, to the 
fact of his having added potash in excess. 
Some months later I made experiments which 
soon began to throw a flood of light upon the 
precise cause of his failure, as well as that of others, 
in producing such results as I had obtained with 
boiled urine and boiled liquor potassz. 
I chanced to look one day at the fifth edition of 
Fownes’ ‘“ Manual of Chemistry,” published in 
1854, a book which I had used as a medical student, 
and on p. 537 found the following statement con- 
cerning urea, “ It is not decomposed in the cold by 
alkalies or by the hydrate of lime, but at a boiling-heat 
it emits ammonia and forms a carbonate of the base.” 
And on the next page there is the statement that 
“if urine in a recent state be long boiled it gives 
off ammonia and carbonic acid from the same 
source.” 
This fact, one must suppose, was unknown to 
M. Pasteur, as in his memoir of 1862, in reference 
to a little chaplet-like organism common in unboiled 
fermenting urine, he said (4oc. czz., p. 52): “Je suis. 

