SUGGESTIONS TO TEACHERS. 459 



(c) Instruments. Every teacher should insist on having at 

 least one good compound microscope. If microscopes are 

 supplied to the class, two students may use one instrument 

 when a full supply cannot be secured, though this is never so 

 satisfactory as to have one student to an instrument. At the 

 outset the teacher should give careful instructions to the stu- 

 dent in the use and care of the compound microscope. The 

 laboratory should also supply dissecting pans of heavy tin, six 

 by twelve inches, with flaring sides, and one and one-half 

 inches deep. Pour into these a small amount of melted paraf- 

 fin mixed with lampblack. This forms an excellent 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 a dozen or so flat-bottomed 

 watch glasses. 



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 

 beginners' 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 transferred 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 preservative 

 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 incor- 

 porated institutions, by application to the collector of internal 



