52 Proceedings of the Royal Irish Academy. 



of the ferment were narrow and elongated, very like the particles found in 

 sour milk. 



After a long and careful research, Pasteur showed that these unknown 

 ferments were really living organisms, low forms of vegetable life growing 

 freely in the liquids, and causing the characteristic fermentation changes as 

 a result of their growth. 



The alcohol in wine or beer is produced from the sugar of the grape (or 

 the starch of the barley or potato after it has been changed into sugar) by 

 the working of a living organism — yeast. The formation of acids in the 

 manufacture of vinegar or the souring of wine is due to the action of a 

 different living organism. Pasteur clearly established that these fermentations 

 were intimately associated with the presence of certain low forms of life ; 

 and that when a fermentation failed, it was because the organism responsible 

 for the change was either absent altogether or unable to grow properly. 



He studied and isolated the ferment which causes milk to turn sour, and 

 is now familiar to science as the Lactic Bacillus. 



These results, part of which was first published in 1857, were revolutionary 

 in their consequences. Dr. Horace Brown, a great authority on the 

 fermentations, wrote of them : 



" The current of my thoughts was entirely changed by the perusal 



of the earlier work of Pasteur Few here can realize what it meant 



to have the vague and utterly sterile ideas of the Liebig school replaced 

 by the clear and logical demonstration that fermentations are phenomena 

 correlative with the vital action of specific organisms." 



Thus was demonstrated a great scientific discovery of the last century : 

 Fermentation is one of the manifestations of life. It has been abundantly 

 shown that this applies to all the natural fermentations known to man. 

 Pasteur was the first scientific vitalist in that he replaced the confused notion 

 of obscure and indefinite chemical forces by the clear notion of definite 

 living organisms. Looking back from the quiet haven of established and 

 accepted knowledge, it is easy to underestimate the importance of this 

 discovery ; but to anyone acquainted with the desolate confusion of ideas 

 which existed at the time of Pasteur's researches, his work rises like a light- 

 house above an uncharted and unresting sea — a lighthouse set upon the rock 

 of truth, which for Pasteur was as the Rock of Ages. 



III. 



In 1859 Pasteur's eldest daughter died. One of his letters written at 

 that time contains the following sentence : — 



" Let us think of those who remain, and try as much as lies in our 

 power to keep from them the bitterness of life." 



