AIDS TO BACTERIOLOGY 



CHAPTER I 

 INTRODUCTION 



THE Thallophyta, which form the lowest group of cryp- 

 togainic plants, show no division into root and stem, and 

 have no fibre- vascular system. They are divided into 

 algae, which contain chlorophyll, and fungi, which contain 

 none. Excluding the Hymenomycetes (mushrooms, etc.), 

 the fungi are microscopic, and most genera and species 

 come within the purview of bacteriology. The Hypho- 

 mycetes (moulds) and the Blastomycetes (yeasts and 

 torula) receive frequent attention from the bacteriolo- 

 gist, and Chapters XV. and XVI. are devoted to them. 

 While the study of bacteria, or Schizomycetes, is the 

 primary object of bacteriology, its scope has gradually 

 extended beyond the fungi to include organisms too 

 small to be seen with the microscope (ultra-microscopic 

 organisms) and such unicellular animals (Protozoa) as 

 cause disease in man, beast, or plant. Of vital impor- 

 tance is a knowledge of the circumstances under which 

 organisms die, so disinfection occupies a prominent place 

 in the science. 



Anatomy. The cell wall is a true membrane (Ellis and 

 Meyer), and is generally composed of a nitrogenous sub- 

 stance very similar to chitin, a skeletin not found in 

 vertebrates, but of frequent occurrence in the cuticles of 

 invertebrates. 



The cell membrane in many, perhaps all, forms some- 

 times swells to form a capsule. Large numbers of bac- 

 teria may cluster together in a jelly-like mass known as a 

 zooglosa. 



The cell contents, or cytoplasm, consists of translucent 

 protoplasm. Scattered through the cell or massed at the 

 poles of certain bacteria are granules that stain differently 



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