14 OUTLINES OF BACTERIOLOGY 



L Protoplasm. As in all other organisms, so in bacteria this is a 

 semi-liquid, semi-solid substance. It can be stained with the usual 

 dyes, the best in the case of bacterial protoplasm being solutions of 

 methylene-blue, iodine, Bismarck-brown, or fuchsin. In higher plants 

 increase of the volume of the cell is more than the protoplasm can 

 keep up with, and consequently spaces, called vacuoles, are left in the 

 cell, which are not filled with protoplasm. The vacuoles are filled with 

 cell-sap, which consists usually of a mixture of raw materials, designed 

 for the building up of fresh protoplasm, and other materials produced 

 by the breaking down of protoplasm. Vacuoles have been demonstrated 

 in bacterial cells (Fig. 23), and we may reasonably assume that they 

 are filled with substances of the same class as the vacuoles of the 

 higher plants, though this cannot be demonstrated. The protoplasm 

 can be made to contract from the cell-membrane which encloses it 



Fig. 23.— Cell allowing Fia. 24. — Plasmolysed cells, 



vacuoles. Shows clear space between 



wall and protoplasm. 



by placing the organism in a substance like common salt, which 

 abstracts a portion of the water from the protoplasm (more than 75 per 

 cent, of protoplasm consists of water). This causes it to contract, thus 

 separating it from the membrane (Fig. 24). A cell thus treated is said 

 to be plasmolysed. 



With regard to the specialised portions of protoplasm, the first we 

 have to deal with is the nucleus. Many and various are the opinions 

 which are held with regard to the presence or absence of this organ, 

 but we need not enter into the numerous views entertained on this 

 subject. It will be suflScient to mention that by appropriate staining 

 it is possible to demonstrate small round substances alv,rays enclosed 

 in protoplasm, which, in number, relative size, and staining capacity, 

 correspond to similar structures which are found in the cells of fungi. 

 It is probable that these are nuclei, but since other small round sub 

 stances are often found in the cell, which we know are not nuclei, 

 and which stain in a similar fashion, there is a certain amount of 

 uncertainty, the more so because these are too small to admit of their 



