94 THE MICROSCOPE. Jul) T , 



QUESTIONS ANSWERED. 



Note. — Dr. S. G. Shanks, of Albany, X. V. . kindly consents to receive all sorts of ques- 

 tions relating to microscopy, whether asked by professionals or amateurs. Persons of all 

 g ades of experience, from the beginner upward, ate Welcome to the benefits of this depart- 

 ment. The questions are numbered Jor future r ef ere rice. 



158. What is " Gage's" method for staining blood corpuscles f 



— N<> rice. 



The following is Professor Gage's method: Three or four 

 drops of fresh blood are allowed to fall into 10 c.c. of a f per 

 cent, solution of salt ia water, and well stirred to separate the 

 corpuscles ; add 100 c.c. of a saturated solution of picric acid 

 in water, constantly stirring; allow the corpuscles to settle, 

 pour off the liquid, add an equal quantity of the salt solution, 

 settle, decant again, and repeat this washing until the salt 

 solution is but faintly tinged with the picric acid ; decant at 

 last as completely as possible ; add 10 c.c. of a mixture of 

 5 parts of Frey's carmine and 95 parts of picro-carmine solu- 

 tion, or the picro-carmine solution alone, and stain 1 to 15 

 hours. Examine a drop occasionally, when sufficiently 

 stained, settle, pour away the staining fluid, and add 10 to 15 

 c.c. of a mixture of glycerine, 100 c.c, and acetic acid 1 c.c. 

 Preserve and mount in this last fluid. 



159. What is the nature of the pygidium of a flea, referred 

 to in catalogues as a test-object f — P. W. G. 



The pygidium is an oval-shaped organ on the last abdom- 

 inal segment of the flea ; there are about twenty-six disks, 

 each exhibiting a long, central filament, and between the 

 disks are many minute bulbed bristles. These filaments and 

 bristles are the particular test-objects to be observed. They 

 vary in appearance, according to the illumination. The pygi- 

 diumi s supposed to serve the flea as an organ of hearing. It 

 is no longer used as a test, having been supplanted by other 

 objects of more uniform structure and appearance. 



160. Can you give a complete formula for an amateur to try in 

 making Farrant's solution f — S. 



Boil an excess of arsenous acid ('white arsenic) in water to 

 make a saturated solution ; cool and filter. To 4 ozs. of this 

 solution add 4 <»zs. of picked gum arabic, and let it dissolve 

 completely in the cold. Then add 4 ozs. of pure glycerine. 



