324 STUDIES IN ADVANCED PHYSIOLOGY. 



large quantities as a preserving fluid for anatomical and 

 zoological specimens. 



It is produced by a process called fermentation. This is 

 a process brought about by a little plant called the "yeast 

 plant," which by its action upon sugar converts it into 

 alcohol and carbon-dioxide gas and several minor products. 

 In the distillery or the brewery this process of fermenta- 

 tion is allowed to go on until the desired per cent, of alco- 

 hol has been reached. The carbon dioxide gas is allowed 

 to escape, and gives to the fermenting vats their frothy or 

 "brewing" appearance. The condition of things in the 

 making of yeast bread is the same. Here, too, some yeast 

 which has either been specially put in, or else allowed to 

 fall in from the air, acts upon some of the sugar in the 

 dough, resulting in the formation of alcohol and carbon 

 dioxide gas. The carbon dioxide gas in its attempt to 

 escape from the dough forms innumerable little bubbles 

 throughout it, and so causes the bread to "rise" or become 

 light. The alcohol, of course, evaporates in the process of 

 baking. The same thing is again illustrated in the famil- 

 iar canning of fruits. Here the fruit to be preserved is 

 boiled, the primary intention of which is to destroy all 

 germs and all yeast plants in it, and then the fruit before 

 it has a chance to cool is put into jars and these then her- 

 metically sealed. If, however, the sealing is defective and 

 air, as we say, gets in, fermentation is soon set up and the 

 sugar in the fruit is ushered along in the process towards 

 the formation of alcohol and remoter substances. It is not, 

 however, the air which sets this process going. It is the 

 introduction of some yeast plants along with the air which 

 is the source of the trouble. 



The chemical and physical properties of alcohol in its 

 various forms need not be dwelt upon here, the primary 

 question in this instance being its physiological effects. 

 This, in a general way, is its apparent stimulating power. 

 Administered to animals it quickens, for a while at least, 

 the general tone of nearly all the organs. It produces a tem- 



