'200 TRANSACTIONS OF THE ttORTTCtri.TURAL 



question. He examined 3'east and the mnst of beer and other ferment 

 substances, and found the "thick, pasty fluid to consist of grayish 

 gh)bules from s^VTy to tows of an inch in diameter. As soon as fer- 

 mentation begins these corpuscles move about in all directions, en- 

 large and l)ecome covered Avith ])rojections, which finally drop oft' 

 and become independent corpuscles, and repeat the same operation 

 so as to increase the quantity of yeast to an extent limited only by 

 the quantity of malt infusion employed." Here we have a perfect 

 picture of vegetation of the lowest order of organic life, viz: a 

 simple protiferation of cells, the reproduction being by budding — 

 not by fruiting. 



At this point the subject rested mainly, and was almost forgotten 

 until about the year 1838, when Schwann and others revived the 

 c[uestion, and to microscopic examinations added many interesting 

 and satisfactory experiments, all of which went to prove that the 

 microcosm already described was a true and distinct vegetable organ- 

 ism, that it flourishes best at a temperature ranging from 68° to 75° 

 Fahrenheit, that the vitality of its germs is destroyed by a boiling 

 heat, and that said germs may be, and often are, supplied by the 

 atmosphere in Avhich they float, like the germs of other fungi. 



It seems that it is not the simple presence of the yeast plant in 

 the proper media which causes fermentation; it is in the vegetative 

 process in active progress that the fermenting principle is evolved, in 

 like manner as the germination of barley yields diastase, by the in- 

 fluence of which starch is converted into sugar in the process of 

 malting. In fact, " in hread-making some of the starch is converted 

 into dextrine and this into sugar by the ferment.*' Thus is our 

 analogy between the malting of barley and the ferment of the yeast 

 plant supported. 



This much for theory. As a practical fact, every housekeeper 

 knows tlyat ferment, in the form of dried yeast, may be kept dor- 

 mant for an indefinite period, but when placed in the presence of 

 moisture (she soaks her yeast cakes) and a moderate degree of 

 warmth (she sets it near the fire) it becomes an aefire ferment, capa- 

 ble of transmitting its quality ("the leaven leavens the whole 

 lump") without limit. She knows that if her bread or yeast is set 

 in too hot a place it is scalded and its rising quality killed (the germ 

 of the yeast plant is killed). She knows that if her cans and jars 

 of fruit are not sealed ^Mjoiling hot," the most careful previous 

 cooking will not prevent their being spoiled by fermentation. (The 

 cool air re-entering before the can is sealed brings fresh live germs 

 of fungi with it. ) She knows that if light as well as air is not ex- 

 cluded, mould, an n'rial-growhifi fungus, will very likely make its 

 appearance upon the surface of the fruit. ( The yeast plant only 

 flourishes when merged or submerged- in fluid or semi-fluid substances. ) 



This brings us to another and very different fungus which the 

 fruiterer has to contend with. As moderate boiling does not pre- 



