158 CLASSIFICATION OF THE MICEO-OBGANISMS. 



are about to undergo fission. The nutriment has also a 

 certain influence ; according to the medium in which 

 the species in question is cultivated, and according to 

 the more or less favourable state of all the conditions of 

 life, slight differences in size and thickness appear, and 

 fully developed or stunted individuals are formed. As 



a I c d e f g 



Fig. 34. Individual morphological differences dependent on age 

 and nutriment X 700. 



f, cocci. Various conditions of age and nutrition of the same species. 



b c, various conditions of age of two species of bacilli. 



d e, modifications of one species of bacillus dependent on the nutritive 

 conditions. 



/ ff, modifications of another species of bacillus dependent on the nutri- 

 tive conditions. 



these factors, however, are of relatively slight intensity, 

 none of them as a rule destroy the peculiar morpho- 

 logical character of the species ; in spite of the modi- 

 fications induced by age and food, certain character- 

 istics, as for example the relations between longitudinal 

 and transverse diameter, the form of the ends of the rod, 

 &c., are so completely preserved in the majority of the 

 individuals that they are thereby sufficiently characterised 

 morphologically. 



structure of All bacteric cells consist of cell membrane and cell 

 the fission* contents. The latter have the appearance of ordinary 

 fungi. protoplasm, are as a rule colourless, except income forms 



recently discovered by van Tieghem, which contain 

 chlorophyll, as well as some putrefactive organisms 

 stained red by the so-called bacterio-purpurin. Small 

 oil globules are often observed in the cells ; at times also 

 dark, highly refracting bodies, which consist of sulphur 

 (beggiatoa and red putrefactive organisms). Some 

 bacteria assume a blue colour on the addition of iodine, 

 and thus show the presence of granulose ; this reaction 

 is especially marked in the stage preceding the forma- 

 tion of spores. Nuclei are not found. When the cells 

 degenerate and die a marked turbidity and granular 

 degeneration of the protoplasm occurs. 



The cell membrane, which must be very extensile in 



