150 CONCERNING PRESENT 



which I knew that Bacilli or any such organisms did not originate ; 

 though I had ascertained that the inoculation of boiled urine with 

 these spores when they had not been previously heated would 

 cause Bacilli to grow and multiply therein most freely. An 

 emulsion of the old spores was made by scraping the dried scum 

 from the glass slips into a small quantity of water, followed by a 

 vigorous shaking. Drops of this emulsion were then added to 

 some acid urine, and this inoculated fluid was subsequently 

 boiled for twenty minutes, with the result that the spores in- 

 variably seemed to be killed — seeing that the fluids remained un- 

 changed. 



Thus, boiling for twenty minutes in a slightly acid fluid seems 

 to destroy the actual spores, while boiling for five hours is said to 

 be necessary in another neutral fluid (hay infusion) to ensure the 

 destruction of similar spores possibly present. This, of course, 

 may be true, or it may not. Spores actually existing in the hay 

 infusion may be much more speedily killed ; and it may be the 

 power of giving birth to organisms (the germinality of the fluid) 

 which requires the five hours at ioo° C. for its extinction. 



It is true that there is good evidence (such as Chamberland 

 advances, and of a kind to which I had long ago called attention) 

 to show that growth and multiplication of Bacilli does not take 

 place so freely or quickly in slightly acid as in slightly neutral 

 solutions. But then might not, even ought not, the same difference 

 to hold good in regard to the possible origin of living units in the 

 respective fluids ? The conditions less favourable for growth 

 should be less favourable for origin, and vice versa. 



The difference between twenty minutes and five hours of 

 exposure to ioo° C. is enormous ; but the difference between the 

 rate of growth and multiplication of Bacilli in slightly acid and in 

 slightly neutral fluids respectively, however real, is comparatively 

 insignificant. 



Hence the question of the possible germinality of the hay 

 infusion cannot be ignored. But here again, as ever, we cannot 

 completely get rid of the doubt, that in my death-point experiments 

 the spores were not really killed by the twenty minutes' boiling 

 in the acid urine. Chamberland might retort that they may have 

 been merely rendered inert by the heat so long as they remained 

 in this fluid. To attempt to get rid of this difficulty is to come 

 face to face with its correlative, namely, how are we to decide, 

 when deaUng with other more favourable fluids, whether an 



