CHAPTER II. 



Morphology l of bacteria Chemical composition of bacteria Classi- 

 fication of bacteria into families and genera Grouping Mode of 

 multiplication Spore-formation Motility The thermal death- 

 point of bacteria. 



IN structure the bacteria are unicellular, always de- 

 veloping from pre-existing cells of the same character 

 and never appearing spontaneously. They are seen to 

 occur as spherical, rod- and spiral-shaped bodies that 

 multiply by the simple process of transverse division, 

 belonging, therefore, to the schizomycetes or fission 

 fungi. 



Under what we are accustomed to regard as normal 

 conditions of development, and by the ordinary methods 

 of examination, bacteria appear very simple in form and 

 structure. They are cells consisting of a protoplasmic 

 mass within a membranous hull that is discernible with 

 more or less difficulty. The protoplasmic body is of 

 material closely allied, chemically speaking, to ordinary 

 vegetable proteid. It is often homogeneous, but in par- 

 ticular species and under various conditions of growth 

 the central mass in stained specimens is commonly 

 marked by the presence of very dark granules, the 

 so-called metachromatic granulations. Again, in other 

 >pccies paraplastic granules giving the microchemical 

 reactions of fat, starch, sulphur, etc., are to be seen. 

 Under certain physical conditions the protoplasmic body 

 presents irregular rents or retractions, the result of pro- 

 teolytic or of osmotic disturbances dependent upon the 



1 Morphology : pertaining to shape, outline, structure. 

 4 49 



