SECTION TWO 



fibres show clearly, in epithelial sheets the cell boundaries are 

 sharply delineated. 



Notes: 



(a) The author states that the presence of light halos and 

 insufficient contrast often constitute a source of trouble when 

 unstained sections are subjected to phase-contrast microscopy; 

 the simple staining procedure described reduces haloing and 

 affords increased contrast. According to the same author, staining 

 for phase-contrast work appears to act advantageously by produc- 

 ing a change in the refractive index of the featureless cytoplasm, 

 the visible cellular structures, or both, and it is probable that 

 methods will be devised to increase the utility of the phase- 

 contrast microscope, thereby facilitating the study of histological 

 and cy to logical details in the same section. 



(b) Readers should also refer to the Luxol fast blue method, 

 which is also due to J. A. Green and is described on page 273. 



Reference: Green, J. A. (1957). 



MacCALLUM'S STAIN 

 For influenza bacilli and Gram-positive organisms in tissues 



Solutions required: 



A. Goodpasture's stain: 



Alcohol 30% . . . . , . 100 ml. 



Basic fuchsin . . . . . . 0-59 gm. 



Aniline oil . . . . . . i ml. 



Phenol crystals . . . . . . i gm. 



B. Picric acid saturated aqueous. 



C. Stirling's gentian violet. 



D. Gram's iodine. 



E. Equal volumes of xylol and anihne oil. 



Technique: 



Tissues should be fixed in Helly and embedded in paraffin wax. 



I. Stain for ten to thirty seconds in Solution A; then wash in 

 tap water. 



281 



