226 STATE BOARD OF AGRICULTURE 



they have noticed that their milk was colored blue, red or green. Bacteria 

 are at work producing pigments of various colors. They evidently secrete 

 a substance which in contact with the oxygen of the air becomes colored. 

 In the water are found several species of bacteria which yield a product 

 of marked fluorescence; various shades may be noticed in the progress 



of their growth. 

 Photogenic There are bacteria which upon cultivation will produce suf- 



Bacteria. ficent light to notc the time of night. There are plants which 

 light up the sea. 

 In the making of bread the yeast plant is added for the purpose of fer-r 

 mentation. It probably gives rise to alcohol and carbonic acid gas; the 

 alcohol evaporates when the heat is applied, and the carbonic acid gas 

 renders the bread light by filling the dough with air spaces in its attempt 

 to escape. 



Contained within cider is a sugar upon which the bacteria 



Zymogenic feed and change it eventually into alcohol, and this alcohol into 



Bacteria. acetic acid. In the evolution of acetic acid other products are 



formed on the way and along with acetic acid. While in many 



ways it is apparently simple, it is,* in reality, a very complex process. 



In the souring of milk, which follows very closely the yeast action in 

 bread and the change of cidt-r in vinegar, the sugar of milk is converted 

 into an acid, called lactic acid, directly or indirectly, as the case may be, 

 and which in turn precipitates or curdles the caseine. 



In swampy districts, underneath the water, there is usually 



^B°^^°^° more or less organic matter in process of decay instituted by 



bacteria. In their operations they eliminate various gases from 



this material. This gas rises to the surface of the water, producing the 



bubbles mentioned. 



This decaying or putrefying process is also found in meat 



^ Bacterid Under another form. Meat is composed of a very complex array 



of elements; a greater complication would be expected in the 



products, which would be somewhat different. The gases formed are of a 



different nature and often give rise to decided odors. Such smells as that 



of ammonia will be noticed, and of rotten eggs, due to hydrogen sulphide. 



Intense poisons may also result from the action of these bacteria 



Toxicogenic and if introduced into the syst«^m will give rise to serious 



Bacteria. trouble. The many fatal cases of poisoning from eating meat 



are generally traceable to decomposing bacteria. 

 The poisoning of milk or ice cream is much the same as meat poisoning 

 and belongs to the same class. 



