ACTERIAL NUCLEUS 



57 



The nuclei of mycobacteria were described as Feulgcn-positive granules, 

 regularly arranged along the length of the bacillus, before it was realised that 

 the bacillus is multicellular, and that each granule was a cell nucleus. Some 

 confusion has also resulted from identification of these granules with those 



Fig. 21 

 EFFECTS OF HYDROLYSIS ON THE SPORE NUCLEUS 



a. Spore with nucleus in natural position. 



b. The " crescentic nucleus." The nuclear material forms a pool between the cytoplasm 

 and spore coat. 



c, d. The " peripheral nucleus." The spore coat is bulged outwards by the ejected nuclear 

 material. 

 e. Complete ejection of nuclear material. 



which appear in the well-known granular or beaded effect seen in heat-fixed 

 preparations of M. tuberculosis. The latter arc, in fact, merely the shrunken 

 cell contents. The metachromatic granules of C. diplitlieria' have also been 

 identified with nuclei by some workers, and disproved by others. They are 

 not seen except in dried preparations, and are artefacts consisting of an aggregate 

 of stainable material within the larger, terminal cells of the bacillus. 



Fig. 20 

 MICROCYSTS OF BACTERIACEM 



The appearance of the resting cell and resting nucleus may be very distincti\e, even in 

 bacteria of which the vegetative stages are similar. Acid-Giemsa, < 3000. 



(1, 2) Bacterium coli. Small, oval cells with an eccentrically staining nucleus. Proteus 

 and most Salmonella are similar. 



(3, 4) Bacterium aerogenes, much larger, with a small, central nucleus. ((4) is stained by 

 methylene-blue-eosin) . 



(5-7) The large microcysts of 5. typhi. 

 < (8) Shigella schmitzii, large oval cells with a central nucleus. 



