MORPHOLOGY, REPRODUCTION, ETC. 11 



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 entoplasm in which is con- 

 centrated the nuclear material. BiitechU ' 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" 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 charac- 

 teristic staining reaction.' 



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

 diphtheria group, Ernst,* Babes,^ and others have demonstrated 

 granular, deeply staining bodies now spoken of as metachromatic granules, 

 or Babes-Ernst granvles, or, because of their frequent position at the ends 

 of bacUli, as polar bodies. These structures are irregular in size and 

 number, and have a strong affinity for dyes. They are stained dis- 

 tinctly dark in contrast to the rest of the bacterial cell with methylene 

 blue, and may be demonstrated by the special methods of Neisser and 

 of Roux.° Their interpretation has been a matter of much difiiculty 

 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.' Again, 

 they have been interpreted as structures comparable to the centrosomes 

 of other unicellular forms. As a matter of fact, the true nature of these 

 bodies is by no means certain. They are present most regularly in 

 microorganisms taken from young and vigorous cultures or in those 

 taken directly from the lesions of disease. It is unlikely that they repre- 



1 Biitschli, " Bau der Bakterien," Leipzig, 1890. 2 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 reddish 

 or purplish hue. 



« Ernst, Zeit. f. Hyg., iv, 1888. » Babes, Zeit. f. Hyg., v, 1889. 



6 See section on stains, p. 107. ' See section on sporulation, p. 16. 



