GENERAL DIRECTIONS FOR PRACTICAL WORK. 



For the examination and dissection of the various specimens the following apparatus will be required : — 



Dissecting Instruments. — Sharp knife or scalpel; forceps; dissecting needles; scissors; and dissecting 

 dish. 



Dissecting needles may be readily made by fastening ordinary needles in penholders. To fasten the 

 needle, hold it in a pair of pliers and push the sharp end into the wood ; withdraw the needle again and insert 

 the blunt end. These needles may be made to cut by grinding edges on them. The needle is readily bent by 

 heating in a gas flame and bending with the pliers. Such needles are very useful in dissecting flowers. 



Dissecting Dish. — A shallow vessel may be used, with a plate of wax, gutta-percha, or black paraffin 

 (prepared by melting down solid parafiin and lampblack) covering the bottom, on which to cut up or pin down 

 the specimen. A tight-fitting lid with a layer of cork fastened to the inside can be used as a dissecting board. 



Optical Instruments. — Microscope ; pocket lens, which may be used also as a dissecting microscope by 

 liaving a fixed rod on which it can be moved up or down, leaving the hands free for teasing, etc. ; watch- 

 maker's niagnifying-glass, which may be used in dissecting out nerves, blood-vessels, or any minute structures. 



Small apertures are best made out by taking a glass tube drawn out to a fine point and blowing through 

 it to enlarge the opening. Bristles can then be readily inserted. 



Reafjents, etc. — Distilled water ; weak spirit ; solutions of magenta, carmine, iodine, salt, potash, and 

 chromic acid ; glycerine ; acetic acid. 



A weak solution of bichromate of potash may be used instead of spirit for preserving. 



A good plan for dropping reagents is to fix glass rods in the corks of the bottles. 



YEAST. 



Mounfinff. — Get some Yeast at the brewer's or the baker's, and place a small drop on a glass slide. Cover 

 with a cover-glass for examination under a high power of the microscope. 



Staining. — Place a little of the staining solution beside the cover-glass, and arrange a slip of blotting- 

 paper at the opposite side, so as to cause a current of the staining material. 



Crushing. — By gentle pressure of the finger or some blunt instrument the wall will burst and the contents 

 flow out. To prevent breaking and dimming of the cover-class it is protected by a tiny pad of blotting-paper. 



BACTERIA. 

 Mince some lean meat and soak in cold water for an hour ; filter, and keep in a warm place for several 

 days ; examine the liquid and the scum which forms on the surface with the highest power of the microscope. 



MOULDS. 



Teasing. — Take a very small portion of the mould and lay it on a slide with a little water, then tease out 

 by means of two dissecting needles. 



PROTOCOCCUS. 



Mounting. — Take a bit of the bark of any tree with green scum upon it, brush off the Protococci and 

 mount in water. 



Mount a drop of water from a water-butt containing Protococci, stain with iodine, which kills the 

 Protococci and renders the cilia visible. 



CHARA. 



Hardening. — A weak solution of chromic acid is used. The chromic acid, in addition to its hardening 

 action, acts also as a solvent, dissolving any limy incrustation. 



imbedding the slender Stem. — Soak a piece with gum, which wiU fill up any cavities ; then harden the gum 

 by dipping in alcohol, which removes water, leaving the stem surrounded by a coat of hardened gum. Place a 



