20 MICROBIOLOGY 



\ 



This outer layer or membrane is thought by some to be a 

 much more concentrated substance than the central por- 

 tion but otherwise the same. With possibly a few excep- 

 tions, it is not known to contain cellulose. 



The presence of the so-called shadow forms which 

 appear as empty capsules and, with species that produce 

 spores, the frequent appearance of a well-outlined cell body 

 after the vegetative form has degenerated in the course of 

 the formation of spores, strengthens the assumption that 

 there is a well-defined cell membrane or wall. 



Cell contents. According to Fischer 1 the cell contents 

 are composed of a substance similar to the membrane or 

 cell wall except that it is not so dense. Biitschli 2 claims to 

 have demonstrated within this entoplasmic substance a retic- 

 ular meshwork, between the spaces of which lie granules of 

 chromophilic or nuclear material. Zettnow 3 states that the 

 contents contain a nucleus, or a substance equivalent to the 

 nucleus of the more highly developed cells, lying w T ithin a 

 net-work of protoplasm. Other observers 4 have confirmed 

 this opinion. Zettnow originally thought the greater part of 

 the organism was of a nuclear nature. The nuclear sub- 

 stance takes the chromatin stain and is often so abundant 

 that the structure holding it is covered up. Whether or not 



1 Fischer. The Structure and Functions of Bacteria. Oxford, 

 1900. 



2 Biitschli. loc. cit. 



3 Zeit. f. Hyg., Bd. XXIV (1897). 



4 Nakanishi. Munch. Med. Wochenschrf., Bd. VI (1900). 



The method of Nakanishi is carried out as follows: Thor- 

 oughly 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 film on the slide should be 

 transparent and sky-blue in color. The microorganisms to be ex- 

 amined 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. 



