282 MICROSCOPY FOR BEGINNERS. 



or katydid, and the gizzard will usually be obtained as 

 an oblong, hard, reddish - brown enlargement attached 

 between the oesophagus and the upper part of the ali- 

 mentary tube below the larger food-sack. Free it from 

 these, cut it open lengthwise, and wash the interior with 

 a camel's-hair brush. View it as a transparent object. 

 The grinding-teeth are well worth studying. The giz- 

 zards of some beetles are also interesting. They, how- 

 ever, are to be dissected out with fine scissors and nee- 

 dles. The work is best done under water. 



9. SCALES OF FISH are obtainable in great variety, and 

 make beautiful objects for low powers. They are often 

 coated with a tenacious mucous material which may be 

 removed by washing in a solution of caustic potassa. 

 They should be examined in water or glycerine. 



10. HAIK. The hair of animals, from the human 

 animal down to the insects, forms an important class of 

 objects for study. Every animal has characteristic hair 

 that may be recognized if the observer have sufficient 

 skill in the use of the microscope and sufficient knowl- 

 edge of the subject ; but to attempt to identify hair de- 

 mands careful work with high powers. It cannot be 

 done with a pocket-lens, nor with a one-inch objective, 

 unless the specimen is extremely common, and the ob- 

 server has examined it often and attentively. The dif- 

 ficulty is increased by the fact that the hair of our small 

 mammals differs greatly in microscopic structure in dif- 

 ferent parts of the body. I once heard a lecturer claim 

 to have identified an unknown sample of hair with a 



