$6 BACTERIA. 



possess has only gradually been accumulated. These cells 

 are composed of a granular protoplasm surrounded by a 

 definite envelope. When these vesicles or cells are watched 

 during their development, growth, and multiplication, there 

 may be seen, at or near one or other extremity of each, 

 small protoplasmic bodies, which are projected beyond the 

 general outline of the cell, and which gradually but surely 

 increase in size. Ultimately there is a constriction, more 

 or less marked, between the original cell and the bud, and 

 the bud grows to the size of the parent cell ; the same 

 process is repeated time after time, until there is formed 

 a chain or series of ellipsoidal or rounded yeast-cells. At 

 one time it was supposed that there was no development 

 either of spores or of mycelial chains, but, thanks to the 

 researches of Reess, by whom the presence of spores within 

 the cells of certain forms of yeast was demonstrated, and to 

 those of Hansen, who was able to confirm their observations 

 as regards spore formation, and also to demonstrate the 

 presence of typical chain mycelia as well as of the budding 

 form of mycelium, these organisms have been put into a 

 separate family by botanists, who have given them the name 

 of Saccharomyces, sugar fungi, or yeasts. These saccharo- 

 myces are indeed to be looked upon as fungi, for although 

 they are closely related to the algas in many respects they 

 contain no chlorophyll. 



Many of the later observers made very definite statements, 

 founded apparently on very accurate data, that the process of 

 alcoholic fermentation is closely bound up in the question of 

 organized ferments ; nevertheless Liebig continued to defend 

 his doctrine of unorganized ' ferments with great ingenuity 

 and vigour. His theory was that fermentation was the result 

 of " internal molecular motion which a body in the course 

 of decomposition communicates to other matter in which the 

 elements are connected by a very feeble aflSnity " (Schiitzen- 

 berger, on Fermentation, p. 40). " YeaSts, and in general 

 all animal and vegetable matter in a state of putrefaction, 

 will communicate to other bodies the condition of decom- 

 position in which they are themselves placed. The motion 

 which is given to their own elements by the disturbance 

 of equilibrium is also communicated to the elements of 



' The term unorganized is not here used in its modern signification, 

 which will be mentioned in the next chapter. 



