536 ZOOLOGY 



bottom for pinning specimens to be dissected. There should also be a bone 

 cutter, a syringe with rubber tubing and glass canulas for injecting the blood vessels, 

 a supply of small pipettes, a few pipettes with large bulb, and two or three flat- 

 bottomed watch glasses for each student. 



Each pupil should have, in addition, a good hand lens; a scalpel; a pair of fine- 

 pointed scissors; a pair of forceps; a probe; dissecting needles; a small supply of 

 glass slides and cover-glasses. 



{d) Reagents. — The number of necessary reagents for a beginner's course is not 

 large. The following are the most essential. 



Preserving Reagents. Alcohol. — This is the most used of all reagents. It is a 

 preserving fluid. It hardens organic matter by withdrawing the water from it. 

 Commercial alcohol is usually of a strength of about 90 to 95 per cent. Specimens 

 should first be placed in 50 per cent, alcohol and then in a day or two be trans- 

 ferred to a stronger grade (70 per cent.). After such treatment they may be 

 preserved permanently in a strength of 70 to 80 per cent. Plenty of the preserva- 

 tive must be supplied, and care must be taken that it does not lose too much 

 strength by evaporation. Animals must be opened, so that the fluid may the more 

 quickly enter the cavities. 



Alcohol may be secured free of the revenue tax by incorporated institutions, by 

 aiiplication to the collector of internal revenue of the district in which the school 

 is located. Application should be made several months before the alcohol is 

 needed. 



Formalin has been much used in recent years as a substitute for alcohol, or 

 in combination with it, as a preservative. It is a 40 per cent, solution of formalde- 

 hyde in water, and be further reduced by adding water. A 10 per cent, solution of 

 formalin is made by taking 10 parts of commercial formalin and adding 90 parts of 

 water. This fluid will safely preserve materials through the term. The same care 

 must be observed as with alcohol. The specimens should be washed in water 

 before studjring, as formol is irritating to the mucous membranes of nose, throat, 

 and eyes. 



Killing Reagents. — Choloroform is usually used as a stupefying reagent. Air- 

 breathing animals exposed to its fumes are soon rendered unconscious, and die in 

 a relaxed condition. 



Minute water animals as Hydra, Dero, and the like, are often advantageously 

 killed by sudden immersion in hot water or hot corrosive sublimate (saturated solu- 

 tion). 



Staining Reagents. — A few stains are of advantage, if there is any attempt to 

 study tissues or the Protozoa. 



Magenta (aqueous solution). One part by weight of the dry magenta or fuchsin 

 in 100 parts of water. Stains fresh tissues well, but is not a nuclear stain. 



Methyl green; i per cent, aqueous solution. Add one part of acetic acid to 100 

 parts of this. The resulting fluid is a superior nuclear stain for elementary 

 work. 



Mounting Reagents. — Water, alcohol of different strengths, glycerine, and 

 normal salt solution ( ^i per cent, solution of common salt) are the more commonly 

 used materials for temporary mounting of objects to be examined under the 

 microscope. The normal salt solution is especially valuable for delicate fresh 

 tissues, blood, and the like 



The teacher, if inexperienced in technic, must consult works on microscopical 

 methods for information about the making of permanent mounts. 



