30 BACTERIA, GENERAL CONSIDERATIONS, MORPHOLOGY 



FIG. 13 



r : - 



Cell Structure. The cell which forms the body of a bacterium does 

 not show any well-marked differentiation into a protoplasmic body 

 and a nucleus. Most of the substance of the bacterium, however, 

 takes the so-called nuclear stains, particularly the basic anilin stains, 

 and extensive studies have shown that most of the body consists of 

 diffusely distributed nuclear substance called chromatin. The latter 

 is not contained in a well-defined nuclear membrane, as in cells of 

 higher plants and animals, but is intimately mixed with a scanty 

 amount of protoplasm called the entoplasm, around which there is often 

 a very small rim of ectoplasm. In certain very young bacteria, or in 

 bacteria which are at rest and not dividing a small nucleus-like body, 



can sometimes be demonstrated, 

 but in all actively dividing bac- 

 teria the chromatin fills the 

 interior of the cell and is present 

 to such an extent that it almost 

 completely hides the scanty 

 amount of entoplasm. 



Bacteria often contain distinct 

 granules which in the unstained 

 condition are highly refractive, 



\ / and when stained take the dye 



in a very intense manner. 



^JtjjJL m These granules are known as 



the metachromatic bodies or the 

 polar bodies, since they are found 

 at one or both ends of a bacillus. 

 They are also called the Babes- 

 Ernst granules, after the two in- 

 vestigators who first described 

 them minutely. These polar 

 bodies must not be confounded with the sporogenous granules (see 

 below). 



The ectoplasm of the bacteria does not usually stain by the 

 ordinary methods used. While generally scanty, the ectoplasm may 

 be more powerful, particularly in bacteria with many flagella (see 

 below). It is believed, and perhaps fairly well demonstrated, 

 that bacteria generally possess a membrane between the ectoplasm 

 and the endoplasm, and, as a rule, some, under definite conditions, 

 possess outside of the ectoplasm a smaller or larger gelatinous 

 capsule surrounding the bacteria. The jelly-like masses forming 

 these capsules may become confluent, and so form one gelatinous 

 matrix in which the bacteria are embedded like cells of higher 

 animals in an intercellular substance. Such formations are known 

 as zoogloea or zoogloeal masses. 



Flagella. If we study various bacteria in the live state in a drop 

 of water or other suitable fluid we will notice some that possess the 



Postmortem smear from the heart blood 

 in a case of bubonic plague, showing one 

 plague bacillus in the centre of the field, with 

 polar bodies stained very deeply. X 2000. 

 (Author's preparation.) 



