26 



DE. BASTIAlf ON THE 



failure has as yet attended the efforts of others to reproduce 

 these very delicate though crucial experiments. 



At an early stage of this investigation experiments were 

 made by me to test the relative effects of different amounts of 

 liquor potassae in such experiments as I have just described. I 

 found that if only two or three drops of this fluid were added 

 from a similar tube to a quantity of boiled urine when, in accord- 

 ance with the directions previously given, it w^ould have required 

 10, 12, or more minims, such a specimen of urine was never 

 fertilized. This convinced me fertilization in the other cases 

 was not due to the survival of germs either in the liquor potassae 

 or in the small amount of air within the liquor-potassse tube, and 

 consequently that the heat to which this had been submitted had 

 been quite sufficient to sterilize its contents. One drop of this, 

 as of any other fluid, if it really contained living germs, would 

 always suffice to infect many ounces, a gallon or more of urine. 



The same conclusion, viz. that the contents of the liquor- 

 potassse tube had been completely sterilized, was also forced 

 upon me by the fact, which I frequently verified, that an excess 

 of liquor potassse to the extent of 1 or 2 minims beyond tlie 

 proper proportion would also invariably cause the urine to re- 

 main sterile in these experiments with airless vessels — a result 

 which would have been impossible if living germs had really been 

 contained within the liquor-potassae tubes. A slight excess of 

 liquor potasssB was, in fact, soon found to be rather more inhibi- 

 tory in dealing with airless flasks than it had been when experi- 

 menting with flasks whose necks were plugged with cotton-wool — 

 as in those of my tentative first series, in which the fluids were, of 

 course, exposed to the influence of atmospheric oxygen. It was 

 in consequence of this, and because on trial I have found that 

 a slight deficiency of liquor potassae was comparatively harmless, 

 that in the paper sent to the Eoyal Society last year, of which an 

 abstract only has been published, I counselled the addition in the 

 plugged-flask experiments of § of the quantity of liquor potassae 

 which would have been needed for neutralization before boiling, 

 and in those with closed airless vessels its addition to the extent 

 of f of such quantity. 



In relation to the variable period of fertility, to which I also 

 called attention in the paper above mentioned, as occurring in 

 my earlier experiments, it may be well to quote the following re- 

 marks : — " This variability might, I think, be in a great measure 



