MORPHOLOGY, REPRODUCTION, ETC. 11 



matcly intermingled with the cytoplasm. The opinion now held by 

 most observers who have studied this phase of the subject favors 

 the existence of an ectoplasmic zone which includes cell membrane 

 and flagella, but is definitely a part of the cytoplasm, and an ento- 

 plasm in which is concentrated the nuclear material. Biitschli* 

 claims to have demonstrated within this entoplasmic substance a 

 reticular meshwork, between the spaces of which lie granules of 

 chromophilic or nuclear material. Confirmation of this opinion has 

 been brought by Zettnow 5 and others. Nakanishi, working with a 

 .special staining method, asserts that some microorganisms show 

 within the entoplasmic zone a well-defined, minute, round or oval 

 nucleus, which possesses a definitely characteristic staining reaction. 6 

 In the bodies of a large number of bacteria, notably in those of 

 the diphtheria group, Ernst, 7 Babes, 8 and others have demonstrated 

 granular, deeply staining bodies now spoken of as met achromatic 

 granules, or Babes-Ernst granules, or, because of their frequent posi- 

 tion at the ends of bacilli, as polar bodies. These structures are 

 irregular in size and number, and have a strong affinity for dyes. 

 They are stained distinctly dark in contrast to the rest of the bac- 

 terial cell with methylene blue, and may be demonstrated by the 

 special methods of Neisser and of Roux. 9 Their interpretation has 

 been a matter of much difficulty and of varied opinion. Those who 

 first observed them held that they were a part of the nuclear material 

 of the cell. Others have regarded them as an early stage in spore 

 formation, or as arthrospores. 10 Again, they have been interpreted 

 as structures comparable to the centrosomes of other unicellular 



*Biitschli, Bau der Bakterien," Leipzig, 1890. 



5 Zettnow, Zeit. f. Hyg., xxiv, 1897. 



'The method of Nakanishi is carried out as follows: Thoroughly cleansed 

 slides are covered with a saturated aqueous solution of methylene blue. This is 

 spread over the slide in an even film and allowed to dry. After drying, the slide 

 should be of a transparent, sky-blue color. The microorganisms to be examined are 

 then emulsified in warm water, or are taken from the fluid media, and dropped upon 

 a cover slip. This is placed, face downward, upon the blue ground of the slide. In 

 this way, bacteria are stained without fixation. Nakanishi claims that by this 

 method the entoplasm is stained blue, while the nuclear material appears of a red- 

 dish or purplish hue. 



1 Ernxt, Zeit. f. Hyg., iv, 1888. 



8 See section on stains, p. . 



9 Babes, Zeit. f . Hyg., v, 1889. 



10 See section on sporulation, p. 16. 



