THE FISSION PLANTS. 65 



the Bacteria may exist for indefinite periods of time, and 

 will endure much higher temperatures than the ordinary 

 forms. In this condition they are wafted about from 

 place to place in the air. When they meet with condi- 

 tions favorable to the life of the organism the spores 

 develop into cells, which multiply by the usual process 

 of fission. 



Bacteria occur everywhere, accomplishing both good and ' 

 harm. The air, in its purest condition, contains numerous 

 spores. Putrefaction and fermentation of all kinds are 

 brought about by the direct agency of these organisms. 

 It is settled beyond dispute that many infectious diseases 

 are caused by Bacteria. Other Bacteria are not only 

 harmless but are believed to be essential to life in aiding 

 jiL-the digestion of the food. Some are profitably culti- 

 vated and sold to the makers of butter and cheese for 

 producing desired states and conditions. Other forms 

 are absolutely essential to the life of the higher plants 

 in bringing about nitrification in the soil, thereby furnish- 

 ing food materials for plants. 



Bacteria exert a very important influence on the sub- 

 stances in which they grow. In the case of the pathogenic, 

 or disease-producing Bacteria, by-products, known as pto- 

 maines and toxins, are formed. These poisonous products 

 are the active influences in causing the disease. These 

 poisons have been isolated from the bodies of animals that 

 have died of different diseases. When tried on animals 

 known to be capable of taking these diseases, they are found 

 to work with great virulence. Notable instances of toxins are 

 the poisons produced by the Bacteria that cause the changes 

 in fish, meat, and ice cream. It is fortunate, however, for 

 man and animals that the products formed by far the 

 greater number of Bacteria are not poisonous, so that the 

 Bacteria which we are constantly taking into our systems 

 with our food and water only in exceptional cases work 



CLARK'S HOT. 6 



