FERMENTS, FERMENTATIONS, AND LIFE, 545 



acid is produced. Examining with a microscope the casein trans- 

 forming into butyric acid, we observe in it little rods, two thousandths 

 of a millimetre in diameter, and of a length from two to five times as 

 great ; this is the butyric ferment, which, concurrently with other mi- 

 croscopic vegetable growths, determines in various cheeses the slow 

 production of butyric acid and several analogous acids, equally strong 

 in smell. To cite a last illustration, the decomposition of urine, giving 

 rise to an abundant release of ammoniacal gases, is also the result of 

 a fermentation ; under the action of cells smaller than those of brewer's 

 yeast, the contained urea changes to carbonate of ammonia, rendering 

 the liquid highly alkaline and strongly odorous. In short, the fermen- 

 tations we have just described, and many others of the same kind, par- 

 ticipate in the nutrition and development of microscopic beings, of an 

 average size not exceeding some thousandths of a millimetre, and pre- 

 senting the form sometimes of spheroidal or cf egg-shaptd globules 

 (as mycoderms, torulacea), sometimes of straight, bent, or curving 

 rods (as vibrios and bacteria). These diminutive beings engender the 

 ferment within the fermenting liquid itself, in the degree and rate of 

 their propagation in it. 



There is another class of fermentations in which the immediate 

 presence of definitely-shaped corpuscles cannot be traced. Thus di- 

 astasic fermentation consists in the transformation of starch into sugar 

 under the action of a formless yellowish matter, called "diastase." 

 Amygdalic fermentation is that in which amygdaline becomes the es- 

 sence of bitter almonds, by the action of a like ferment, known as 

 "syraptase." The former takes place in the vegetable embryo when 

 the amylaceous matter of the seed is converted into a soluble sugar, 

 which permeates the growing tissues of the plant. The latter occurs 

 when bitter almonds are crushed in water; on contact with the liquid, 

 the mixture of these odorless kernels takes the characteristic smell of 

 the essence of bitter almonds, which results from the fermentation of 

 amygdaline. We regard as fermentations, moreover, a certain number 

 of similar phenomena which can be produced with the implements of a 

 laboratory, and which are constantly taking place in living organisms, 

 of which the cause is a zymotic substance. There exists, for instance, 

 in the saliva a principle called ptyaline, which, like diastase, converts 

 amylaceous matter into sugar. The gastric juice contains another 

 principle, pepsin, which has the eff*ect of liquefying albuminous sub- 

 stances, so that they may be prepared for absorption. The pancreatic 

 fluid contains another principle which acts in a similar way. Digestion 

 is thus reduced to a series of fermentations, as the ancient chemists 

 had rightly conjectured in regard to it. These different phenomena, 

 as well as those in which organisms take part, have the two general 

 characteristics of fermentation ; they occur only within certain limits 

 of temperature, and the weight of the fermentable matter is always 

 much greater than that of the ferment which suffices to decompose it. 



VOL. V. — 35 



