48 CHEMICAL DISCOVERY AND INVENTION 



It is not necessary in this place to peer into the mists of 

 antiquity with the idea of discovering the origin of the pro- 

 duction of an intoxicating drink from barley, in those countries 

 in which the vine was unknown. But it is within the memory of 

 many persons now living, that home-brewed ale was to be found 

 in many country houses, and the practice of producing the 

 beverage at home was one of very long standing, which history 

 tells us may be found recorded in the annals of many centuries. 

 One of the characteristics of the domestic product fifty or sixty 

 years ago was the uncertainty of its quality, and this arose from 

 the state of total ignorance, in which even the experienced 

 brewer then carried on his operations, as to the nature of the 

 process in which he was engaged. It was known that a solution 

 of sugar mixed with yeast undergoes a change, in the course of 

 which it loses its sweetness and, if strong enough, yields a 

 liquid which has an alcoholic flavour and intoxicating properties, 

 but the true nature of yeast was not understood, and it was 

 thought to be merely a form of very unstable albuminous 

 matter. And this idea was supported to some extent by the 

 known fact that a solution of sugar containing vegetable albu- 

 minous matter, as in the case of fruit juices of all kinds, enters 

 into fermentation apparently spontaneously and without the 

 recognised addition of yeast. The state of error was also en- 

 couraged by the introduction of a peculiar theory of fermenta- 

 tion on the authority of Liebig, at the time referred to at the 

 height of his fame. To cut a long story short it may be at once 

 pointed out that by the researches of Pasteur, published from 

 about 1857 to 1861, the facts were established, and the vitalistic 

 doctrine of fermentation placed on a secure foundation. That 

 the yeast which develops spontaneously in a fermenting fruit 

 juice, or which is added to the infusion of malt or wort in the 

 process of brewing beer, is a mass of living matter and that its 

 growth and development are in some way directly connected 

 with the destruction of the sugar in the wort, and the production 

 of alcohol, was the outcome of Pasteur's experimental studies, of 

 which an account is given in his famous book Etudes sur la Biere. 

 But since Pasteur's time many steps have been taken which, 

 while superseding some of his conclusions, detract in no way 

 from the merit of the important pioneering work which he 

 accomplished. 



Ordinary yeast (Saccharomyces cerevisice) when seen under 



