THE ORGANISMS IN YEAST. 219 



contact with the external air involved in the removal of the 

 stopper. But another and more formidable difficulty appears, as 

 to how to ensure the sterilisation of the nutrient fluid. Dr. 

 Charlton Bastian has stated, in his " Beginnings of Life," that 

 even in flasks hermetically sealed, it by no means follows that, 

 because the Hquid (infusion or what not) has been boiled, no 

 development of organisms, and consequently no fermentation, will 

 take place ; in fact, he asserts that the preservation of the liquid 

 unchanged in such flasks and under such conditions is the 

 exception rather than the rule. How, then, is this to be met ? 

 In support of his views, Dr. Bastian brought forward numerous 

 experiments made with infusions of turnip and fresh cheese under 

 the above conditions, by which it was clearly shown that mere 

 boiling by no means ensured the destruction of ferment-life in an 

 organic liquid ; whilst, on the other hand, Pasteur points to flasks 

 of malt infusions which had remained many years ^ — in some 

 instances, I believe, as many as twelve — on the shelves of his 

 laboratory unaltered, although only separated from the internal 

 atmosphere by a plug of cotton wool. In a celebrated lecture 

 delivered some years since, Professor Tyndall showed that infu- 

 sions of hay could not be freed from germ-life by simple boiling, 

 even when continued for several hours, and that such a result 

 could only be arrived at by repeating the process several times 

 with special precautions. It was also found by Cohn that the same 

 thing held good to a greater or less degree with other infusions, 

 and by this observer it was soon noticed that^ whatever species of 

 germ-life might be present before ebullition, any development 

 which appeared afterwards was invariably of the genus Bacillus^\ 

 and that in the absence of organisms of this genus, complete steri- 

 lisation could be effected by boiling. 



It is not necessary now to enter into the question of the germi- 

 nation — if such it be — of Bacillus from spores, for as those liquids 

 which are most suited for our present purpose, rarely seem to 

 contain either Bacillus or its spores, it is not of immediate 

 importance, and so far we may feel satisfied of our ability to 

 destroy the germs of life in our cultivating fluids. Pasteur, in his 



* " Etudes sur la Riere," L. Pasteur, p. 28. 

 t " Quar. Jour. Micro. Science," 1877, p. 83. 



i 



