THE THEORY OF FERMENTATFON. 5 1 



to minute details, and he happily possesses the genius, which has 

 enabled him to arrive at many very interesting and important 

 results. 



M. Pasteur has succeeded in proving that on the external 

 surface of all fleshy fruits when they become ripe, there exists 

 certain minute particles, or germs, which when brought into contact 

 with the ripe juices of the fruits, develop into minute plants, and 

 forthwith grow with great rapidity. These plants are the Yeast 

 Plants, which belong to a great family of microscopic funguses. 

 They are called Saccharomyces^ or Sugar-Eating Funguses, from the 

 peculiar power they possess of decomposing and living upon the 

 saccharine principle of plants, the grape sugar, or Glucose, as it is 

 termed by the chemists, and thus causing their elements to be re- 

 arranged into Alcohol, Carbonic Acid Gas, Glycerine, Succinic 

 Acid, Volatile Acids and other products. 



M. Pasteur obtained these corpuscules, or germs, by washing 

 ripe fruit — grapes he first used — with pure distilled water. The 

 water was rendered slightly turbid by the presence of an infinite 

 variety of minute particles. Under the microscope, many of them 

 were shapeless atoms of dust, scales of epidermis, or spicules of 

 crystaline matter, but many others appeared to be organised cor- 

 puscules, resembling the spores of funguses. These organised 

 corpuscules differed considerably from each other, and when M, 

 Pasteur cultivated them with all due care in saccharine fluids, he 

 found them to swell and germinate at diff"erent times and in differ- 

 ent ways. In an hour, and often in less time, he observed a copious 

 formation of new cells, whilst small bubbles of Carbonic Acid gas 

 were given off, showing that the formation of Alcohol had already 

 begun. They were thus proved to be true Yeast Plants, or Saccha- 

 romyces. M. Pasteur traced the growth of several species of Yeast 

 Plants under the microscope, all differing in their size of cells, 

 shape, mode of budding, and general growth. The most common 

 of these plants, to whose growth in the natural saccharine 

 juices of ripe fruits the formation of Alcohol is chiefly due, he 

 described minutely in 1862, in the Bidletin de la Societ'e Chimique, 

 p. 67. These observations were fully confirmed by Dr. Rees, a 



