CYTOLOGY 



LIFE-HISTORY 



B A C T K R I A 



H: CELL IV ALL STAINS 

 (S, 9, i6, 1 8, 20, 26, 27, 2S, 37, 3S, 39, 45, 53, 56, 66) 



Bacteria arc enclosed in a rigid cell wall which normally resists staining. 

 It may be rendered visible by mordanting in tannic acid, phosphomolybdic 

 acid or cationic detergents. These agents serve the dual purpose of mordanting 

 the cell wall and so altering the protein material ot the cell that it is rendered 

 unstainable and does not obscure the details ot the transverse septa, where 

 these occur. Tannic acid also forms a stainable complex upon the surface 

 of the cell wall, and it it is stained before the mordanting process is complete, 

 this complex may produce an outline picture of the wall, but fail to show 

 internal details. Using 5-10% tannic acid, the wall can be stained with 0-2 °o 

 crystal violet ; with 1% phosphomolybdic acid, i°o methyl green gives the 

 clearest results. The times required for staining and mordanting vary from 

 a few seconds upwards. 



Fig. 3 



THE CYTOLOGICAL 

 STAINING OF COCCI 



(1) Micrococcus cryophiltis 

 by Hale's method for cell 

 walls. Showing two- or 

 four-celled cocci. 



(2) A similar group stained 

 by trichloracetic acid and 

 (jiemsa. Such arrange- 

 ments of nuclear material 

 have been misconstrued 

 as mitotic figures by some 



{Reproduced horn the Jounuil of llaiU-nology) observers. 



The uncierlying cell membrane is not easily demonstrated. Transverse 

 septa derived from it, containing a large protein component, are stainable 

 by simple, basic dyes or by acid-Giemsa, and are sometimes rendered more 

 obvious by fixation with Bouin's solution or similar agents. Bacteria which 

 have been slightly plasmolysed by such fixatives can be stained by 0-050;^ 

 Victoria blue in such a manner as to demonstrate the cell wall and cell membrane 

 simultaneously. 



