Category: L

Device for the visual comparison of coloured fluid with a series of standards of tinted glass set in a revolving circular wheel, only one of which is opposite to the fluid being evaluated at a given time. Various types of standard are available: in bacteriology the phenol red standards disc is of particular value.  

Isotonic suspension medium for bacteria and cells. A mixture of sodium chloride, potassium chloride, calcium chloride and sodium carbonate.  

Broth or agar with a peptone – ox liver base, used especially for the cultivation of Brucella. Thionin and basic fuchsin may be included in modifications for differentiating between the various species.  

Medium for demonstrating lactose femientation, casein digestion or coagulation, and ‘stonny clot’ production in the investigation of clostridial species. Consists of sterile, cream-free milk with alcoholic litmus indicator.  

Bacteria able to utilize carbon dioxide as the only source of carbon. Chemolithotrophs derive energy by the oxidation of inorganic compounds, md photolithotrophs from sunlight. Lithotrophic bacteria are non-parasitic.  

Sodium polyethanol sulphate, 0.05 per cent of which may be added to blood culture broth to destroy the natural bactericidal action of blood.  

Spherical bacillary granules (possibly connected with the storage of carbon and energy) with an affinity for Sudan black or other fat-soluble dyes. The granules appear as blank spaces by Gram or other basic staining methods.  

Method for volutin granules in bacteria and yeasts. Short or prolonged staining of a suspension of the organisms in a very acid solution of toluidine blue results in only the granules (which possess a very strong affinity for basic dyes) taking up the stain, the remainder of the protoplasm staying colourless.  

Rabbit or human blood, 5 per cent, added to molten nutrient agar, mixed and heated in boiling water. The supernatant agar after settling is poured as a medium or Haemophilus species.  

Method for spirochaetes in tissues. The fixed tissue is stained in silver nitrate – pyridine solution, and reduced in formalin – acetone – pyridine, prior to paraffin embedding and section cutting.