STRUCTURE OF BACTERIAL PROTOPLASM. 11 



For the demonstration of the metachromatic granules two methods 

 have been advanced. Ernst recommends that a few drops of Loffler's 

 methylene blue (vide p. 1 08) be placed on a cover-glass preparation 

 and the latter passed backwards and forwards over a Bunsen flame 

 for half a minute after steam begins to rise. The preparation is then 

 washed in water and counter-stained for one to two minutes in watery 

 Bismarck-brown. The granules are here stained blue, the protoplasm 

 brown. Neisser stains a similar preparation in warm carbol-fuchsin, 

 washes with i 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 granules (vide Fig. i, No. 16, the bacillus most to the right), 

 (German, Polkornchen or Polkorner). 



Both the metachromatic and the polar granules have 

 been looked upon by different observers as spores. 

 Against this view, however, is the fact that growths in 

 which they exist show no higher degree of resistance than 

 growths in which they cannot be observed. Further, they 

 do not react to the strict methods of spore staining. Some 

 have considered the metachromatic granules to be evidences 

 of the process of division in the bacterial protoplasm, i.e., 

 of a kind of mitosis. If such is the case they ought to be 

 observed in some members of a growth where active 

 multiplication is going on, and this is not so. The con- 

 ditions in which they occur are in growths where the food 

 material is becoming exhausted, or in growths which have 

 been subjected to unfavourable conditions. Thus they 

 have been observed in bacteria which have been grown 

 for a few days at the most favourable temperature, and 

 thereafter allowed to develop further at less suitable 

 temperatures. It is therefore very probable that the occur- 

 rence of metachromatic granules in a bacterium indicates 

 the onset of degenerative changes. 



In perfectly healthy and young bacteria, moreover, 

 appearances of granule formation and of vacuolation may 

 be accidentally produced by physical means in the occur- 



