BACTERIA AND DISEASE. 



them about the year 1869, after *Hofifman had Bacteria 



demonstrated that these tiny mysteries occu- Explained. 



pied a class by themselves, quite distinct from 



yeast plants and moulds with which they had 



been confused in earlier days of bacteriological 



research. For years scientists had been unable 



to decide as to whether bacteria were members 



of the plant family, or whether they were the 



offspring of animal life, for the reason that 



they were found to possess characteristics of 



both families or kingdoms. When it was dis- Animals or 



covered under the microscope that some of the 



bacteria are spore-forming, their classification 



as members of the plant or vegetable kingdom 



was determined. Absence of chlorophyl, the 



name given to the green coloring matter of 



plants, caused doubt to arise in the minds of 



many; chlorophyl is the property in plant life, 



which enables them to cause decomposition of 



carbon dioxide and ammonia and to consume 



as food their products. Bacteria, lacking this 



property, feed upon the same forms of food as 



the higher animals consume. 



All forms of bacteria may be divided into „ . ^. 



•' Saprophytic 



two great classes in order to simplify for study. Bacteria. 

 These two classes are called the saprophytes, 

 and the parasites. The saprophytes, which are 

 the friends of all animal life, are many times 



* Hoffman was a German botanist. Bpfij at Ro^ 

 jiel?heim, tSi$; died at Giessen, i^i, 

 31 



