THE CHEMICAL COMPOSITION OF BACTERIA 17 



The higher bacteria are those from the Mycobacteriacea up to 

 the yeasts and moulds. They are higher than the Bacteriacea 

 because they tend to form truly or falsely branching filaments 

 and specialized segments, gonidia, which may behave as sex 

 organs. Few of them are pathogenic, except in the genera 

 Mycobacterium and Streptothrix. To the former belongs the 

 diphtheria and tubercle bacillus, both of which are said to have 

 branching involution forms, while to the latter belong the organ- 

 isms of actinomycosis and Madura foot. The Chlamydo- 

 bacteriacea and Beggiatoa are Saprophytes. These require special 

 technique for the laboratory culture. 



The Yeasts or Blastomycetes or budding fungi are next in order. 

 They consist of sharply and doubly outlined, refractive, oval 

 bodies which may grow out into short stalks called mycelia. They 

 grow well in the laboratory and may produce pigments. They 

 are much larger than the bacteria (10-25 /x long). They multi- 

 ply by budding with a separation and removed growth of the 

 young form. They may produce a local or general infection in 

 man, Blastomycosis. They are used in beer making. The 

 commonest genus is Saccharomyces. 



The Moulds or Uyphomycetes represent the next highest group 

 of the plant algae. They are characterized by a greater promi- 

 nence of the mycelium over simple segments or bodies. They 

 are widespread in nature and many are pathogenic. They 

 multiply by segmentation of the mycelia into gonidia or by the 

 development of special spore masses called sporangia. Fur- 

 ther refinements of the spores into sexual elements is known. 

 They are chiefly of interest to the physician on account of the 

 skin diseases that they occasion. 



THE CHEMICAL COMPOSITION OF BACTERIA 



Bodies of bacteria contain water, salts, certain albumins, and 

 bodies that may be extracted with ether. Among the latter are 

 lecithin, cholesterin, and triolein. In acid-fast organisms, fatty 



