80 ^EFFECTS OF TEMPERATURE ON FERMENTS. 



it will yield, as just stated, alcohol and carbonic -acid so long as the tem- 

 perature ranges about 75 ; but, every thing remaining the same, if 

 the temperature be raised to 100 or 120, neither alcohol nor carbonic 

 acid is formed, but in their stead other products arise, such as lactic acid, 

 gum," and manna. Though, therefore, decomposition will go on through- 

 out all this range of temperature, the products will vary very much, al- 

 cohol being formed at a low, and lactic acid at a high degree. 



Again, the decomposition of milk furnishes a very instructive instance. 

 When the temperature ranges from 50 to 75, the liquid turns sour, 

 owing to the formation of lactic acid ; but if the temperature is over 90, 

 the products are different, for now a true vinous fermentation sets in, al- 

 cohol and carbonic acid appearing. It is on this principle that the Tar- 

 tars make an intoxicating liquid from mare's milk. The fermentation of 

 milk, therefore, yields lactic acid at a low, and alcohol at a high degree. 



On comparing these illustrations, the results stand in direct contrast, 

 but both show the great influence which a specific degree of heat exer- 

 cises over such subdivisions ; and, as a consequence of this principle, 

 which obtains equally in the physiological case, we recognize the neqes- 

 sity of maintaining the cavity of the stomach and intestine uniformly 

 at a temperature which is fixed, otherwise there would cease to be any 

 uniformity in the subdivision of the food, occasioned by the digestion 

 there going on. These principles, moreover, lead to the explanation of 

 the action of such stimulating substances as alcoholic liquids,- pepper, 

 etc., which at once determine a local elevation of temperature ; they also 

 explain the injurious effects which may ensue from intemperate draughts 

 of ice-cold water. 



A nitrogenized substance, in a state of change, can thus bring about a 

 definite action on fibrin, coagulated albumen, or casein in the stomach, 

 or on starch in the intestine, so long as a temperature of 100 is main- 

 Loss of power tained, but in every known instance this transmuting power 

 l\ttTmpe * s tota % destroyed by exposure to a very low or very high 

 ature. degree of heat. Large masses of animal matter whole car- 



casses may be preserved for many centuries unchanged if the tempera- 

 ture is kept down to 32. A striking example of this occurs in the case 

 of the extinct elephants which are occasionally thrown on the shores of 

 the Polar Sea from icebergs, in which they have been entombed for 

 many thousand years, their flesh remaining in a perfectly fresh and un- 

 decayed state. And as respects a high temperature, an exposure to 212 

 totally destroys the power. On this principle, all kinds of meat or veg- 

 etable substances may be indefinitely preserved. If such are inclosed in 

 metallic canisters, so as totally to exclude the atmospheric air, and ex- 

 posed to a bath of boiling water, they may then be carried around the 

 world without undergoing any change. 



