12 INTRODUCTORY EXERCISES. 



Application of a reag-ent by irrigation. A drop of the reagent 

 is placed on the slide close to the right edge of the cover, at the 

 opposite edge a piece of blotting paper moistened at the tip is 

 laid in contact with the fluid beneath the cover. Guide the reagent 

 with a glass rod into touch with the mounting fluid, a stream will be 

 established through the preparation towards the blotting paper. Different 

 fluids can be successively brought to bear upon the preparation in this 

 manner. Use small quantities of the reagent and avoid staining the 

 stage of the microscope. 



Irrigate the preparation with Iodine solution, the fibres will 

 be stained of a slightly yellow colour. 



Irrigate, in addition, with strong Sulphuric Acid, the fibres 

 will swell and turn blue ; this is the reaction for Cellulose. 



Linen fibre. (If] The fibres are solid cylinders with a smooth 

 surface. 



Woollen fibre. (//) Cylindrical filaments, the surfaces of 

 which show transverse markings which indicate their structure 

 of imbricated scales. 



Starch granules. Scrape the cut surface of a potato lightly 

 with the edge of a scalpel and diffuse the scraping in water. 

 (//) The oval 1 starch granules exhibit concentric contour lines 

 around a spot placed near one end. Irrigate with Iodine and 

 note the blue colour produced, Iodide of titarch. 



Brownian movement. Rub a piece of Gamboge on a slide 

 in a drop of water until the latter has a yellow tint, cover. 

 (//) Fine particles of various sizes are found which exhibit 

 oscillatory movements. This phenomenon is commonly exhibited 

 by inanimate particles suspended in water. 



Bacteria. (//) Examine a drop of fluid from an aqueous 

 infusion of meat or of chopped straw which has had time to 



1 To ascertain the shape of a small object floating in a fluid, touch the cover 

 with a needle and note any change of configuration whilst the object revolves in 

 the field. 



