GENERAL DIRECTIONS FOR PRACTICAL WORK. 



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



Detecting 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 paraffin 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 

 having 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. 



Reagents, 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. 



Mounting. 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, 

 i 



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 Frotococci 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. 



Embedding the slender Stem. Soak a piece with gum, which will 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 



