16 THE AMERICAN MONTHLY [Jan., 



was made by Mr. Walter H. Bulloch, of this city, and is 

 of the pattern styled by him the ' biological stand.' 



The actual tube length was 8.91 inches from end of nose 

 piece to upper end of draw-tube. 



The cob-web eye-piece micrometer used w^as also made 

 by Mr. Bulloch, the pitch of the screw being ^ millime- 

 ter, and the micrometer head being divided into 200 

 parts, which were read to 1-10 of a division. 



The objective used was a homogeneous immersion 1-1(< 

 made by H. R. Spencer, of Gfeneva, N. Y., having a nu- 

 merical aperture of 1.35, and it was used with a Bausch 

 & Lomb achromatic amplifier, giving an amplification of 

 about 1,500 diameters. The immersion fluid was Prof. 

 Smith's new homogeneous immersion- fluid, the composi- 

 tion of which he has not yet made public. 



The blood w^as drawn from my finger, and a thin film 

 spread with a needle upon the side of a cover-glass from 

 .150 to .165 of a millimeter in thickness, and examined 

 at once, a fresh sample being used upon each occasion. 

 It was examined with central illumination, and always 

 under as nearly the same conditions as possible. Dur- 

 ing the first four days of the examination, I took, night 

 and morning, about one drachm of the elixir of calisaya, 

 iron, and strychnia; during the rest of the time no drug 

 was taken, and the conditions were nearly identical each 

 evening. From 25 to 100 corpuscles were examined each 

 evening, and I have tabulated the results, giving the 

 smallest, largest, and average size, in millionths of an 

 inch, of each 25 corpuscles ; also the average of each 50, 

 75, 100, and 200 corpuscles. The corpuscles were meas- 

 ured, large and small, as they presented themselves in 

 the field of the microscope, the only condition being tliat 

 they should be approximately circular. 



An examination of the above figures shows that the 

 difi"erence between the greatest and smallest averages of 

 25 corpuscles is .000028 or 1-35714 inch, a magnitude 



