TECHNIQUE 9 



E: SIMPLE DYES 



(i, T4, 58, 59) 



Even the simple dyes, especially basic fuchsin and methylene blue, may 

 be ot value upon occasion, it the errors of heat-fixation and drying, which 

 usually accompany their use, can be avoided. The affinity of bacterial 

 cytoplasm for the basic dyes is so great that a short treatment will often 

 produce an appearance ot negative staining of the nuclear structures, which 

 appear pale and refractive against the stained background. This phenomenon 

 is well known, and is usually described as bipolar staining. Accumulations 

 of basophilic material at the poles are also associated with the growth of the 

 cell. Reagents and even displaced nucleic acids may form aggregates in these 

 areas and appear as granular artefacts. 



An interesting refinement in the use oi a simple dye, which has been 

 employed with considerable success, consists in permitting a thin film of 

 carbol fuchsin to dry upon a slide. The bacteria are suspended in a drop of 

 water upon the coverslip which is inverted upon the slide and sealed at the 

 edges. The dye is taken up gradually by the bacteria and the process may be 

 followed under the microscope. 



This method has proved of value in the description o( certain of the 

 complex processes which precede the formation of the resting nucleus, but 

 appears to have failed to demonstrate the active, vegetative condition of the 

 nucleus in the same species of bacteria. 



F: THE USE OF PROTEIN MATERIALS 

 (17, 25, 60, 6r, 62, 63, 64, 65, 68) 



As the surface material, the affinity of which for basic dyes tends to obscure 

 the internal structures of bacteria, is composed mainly of ribose nucleic acid» 

 it has been found possible to digest away this material with the enzyme 

 ribonuclease. This leaves unharmed the deoxyribose nucleic acids ot the 

 nucleus itself, which can then be demonstrated without difficulty. 



