STRUCTURE OF BACTERIAL PROTOPLASM 9 



Neisser stains a similar preparation in warm carbol-fuchsin, washes 

 with 1 per cent sulphuric acid, and counter-stains with Loffler's blue. 

 Here the granules are magenta, the protoplasm blue. The general 

 character of the granules thus is that they retain the first stain more 

 intensely than the rest of the protoplasm does. 



A second appearance which can sometimes be seen in specimens 

 stained in ordinary ways is the occurrence of a concentration of the 

 protoplasm at each end of a bacterium, indicated by these parts being 

 deeply stained. These deeply stained parts are sometimes called polar 



franules (vide Fig. 1, No. 16, the bacillus most to the right), (German, 

 olkornchen or Polkorner). 



With regard to the significance that is to be attached to such 

 appearances, much depends on whether they are constantly present 

 under all circumstances, or only occasionally, when the organism is 

 grown in special media or under special growth conditions. Some 

 bacteria, however stained, show evidence of having the protoplasm 

 somewhat granular, e.g. the diphtheria bacillus. In other cases this 

 granular condition is only seen when the organism has been grown under 

 bad conditions, or where the food supply is becoming exhausted. Some 

 have thought that the appearances might be due to a process allied to 

 mitosis and might signify approaching division, but of this there is no 

 evidence. 



In perfectly healthy and young bacteria, appearances of granule 

 formation and of vacuolation may be accidentally produced by physical 

 means in the occurrence of wha*t is known as plasmolysis. To speak 

 generally, when a mass of protoplasm surrounded by a fairly firm 

 envelope of a colloidal nature is placed in a solution containing salts in 

 greater concentration than that in which it has previously been living, 

 then by a process of osmosis the water held in the protoplasm passes 

 out through the membrane, and, the protoplasm retracting from the 

 latter, the appearance of vacuolation is presented. Now in making a 

 dried film for the microscopic examination of bacteria the conditions 

 necessary for the occurrence of this process may be produced, and the 

 appearances of vacuolation and, in certain cases, of Polkorner may thus 

 be brought about. Plasmolysis in bacteria has been extensively 

 investigated, 1 and has been found to occur in some species more readily 

 than in others. Furthermore it is often most readily observed in old or 

 otherwise enfeebled cultures. 



Btitschli, from a study of some large sulphur-containing forms, con- 

 cludes that the greater part of the bacterial cell may correspond to a 

 nucleus, and that this is surrounded by a thin layer of protoplasm which 

 in the smaller bacteria escapes notice, unless when, as in the bacilli, it 

 can be made out at the ends of the cells. Fischer, it may be said, looks 

 on the appearances seen in Biitschli's preparations as due to plasmolysis. 



The Chemical Composition of Bacteria. In the bodies of 

 bacteria many definite substances occur. Some bacteria have 

 been described as containing chlorophyll, but these are properly 

 to be classed with the schizophyceaB. Sulphur is found in some 

 of the higher forms, and starch granules are also described as 

 occurring. Many species of bacteria, when growing in masses, 



1 Consult Fischer, " Untersuchuugen iiber Bakterien," Berlin, 1894; 

 "Ueber den Bau der Cyanophyceeu und Bakterien," Jena, 1897. 



