1886.] 



MICEOSCOPICAL JOUKNAL. 



25 



brilliant and equally illuminated 

 field. 



The introduction of the new bro- 

 mide paper will be a boon sure to be 

 appreciated to many engaged in mi- 

 croscopical photography. A little 

 wrinkle in using this paper may 

 serve others. Experience soon 

 teaches that all unnecessary handling 

 of the unexposed paper must be 

 cai-efully avoided in order to escape 

 the unsightly spots which record 

 careless fingering. As 4X5 is a fa- 

 vorite size for micro prints, one of the 

 Eastman's film-carriers should be 

 utilized. A piece of 4X5 post-yel- 

 low paper with suitable opening, 

 should be used as a mat. This is first 

 placed in the metal frame ; on top 

 of it the piece of the bromide paper, 

 and the two securely held in place 

 by a piece of glass cut to fit exactly 

 the frame and to replace the wooden 

 carrier. By this means the paper is 

 protected from contact on the edges 

 and held perfectly smooth, while a 

 centered print is insured ; by trans- 

 mitted light the desirable field of the 

 negative can be selected and centered. 



A Contribution to Blood Measure- 

 ment. 



The microscope used in these meas- 

 urements was very carefully made 

 by Mr. Charles Fasoldt, for the pur- 

 pose of comparing and bringing his 

 rulings in accord with the standard 

 inch, as defined by the United States 

 Coast Survey. This instrument was 

 also used to measure and copy the 

 standard centimetre for the American 

 Microscopical Society. 



The stage of the microscope is 

 moved by a standard screw of 100 

 threads to the inch ; the micrometer 

 head attached is divided into 100 

 parts. The eye-piece cobweb-mi- 

 crometer is supplied with two inde- 

 pendently movable spider-lines. The 

 measuring line is moved by a standard 

 screw of 100 threads to the inch. The 

 micrometer head is divided into 100 

 parts. There is also a special index 



to register the number of revolutions 

 of the head. A vertical illuminator 

 with a Bausch & Lomb yV ii""^" 

 mersion objective N. A. 140 was 

 used. 



A Fasoldt standard stage microme- 

 ter was the standard of measurement 

 employed, and by means of the draw- 

 tube the divisions of the eye-piece 

 micrometer was made to correspond 

 to 1-1,000,000 of an inch. 



A ceilain portion of the micrometer 

 screw was used when comparing it 

 with the ruled stage plate, and only 

 that portion of the screw was subse- 

 quently used in measuring the blood 

 corpuscles, thus practically eliminat- 

 ing mechanical errors. In the opera- 

 tion of measuring, the spider-line was 

 placed at a zero point, the blood 

 corpuscle was brought in optical con- 

 tact with it by means of the stage 

 movement, the spider-line was then 

 moved across it and the divisions read 

 off". Frequently the line was moved 

 back, and again read off", to test the 

 accuracy of the first contact. The 

 spider-line was invariably brought to 

 the same zero point for each corpuscle 

 measured. Fresh blood was used for 

 each series of measurements, spread 

 upon a cover-glass in the usual way. 

 A blood corpuscle seen with the ver- 

 tical illuminator presents a novel ap- 

 pearance. It appears smaller than 

 with transmitted light, that is, without 

 coma. It resembles somewhat the 

 yoke of an agg laying on a flat plate. 

 When fresh the corpuscle is smooth 

 and uniform on the surface, but soon 

 a dimple appears, usually excentric ; 

 this enlarges slowly until, within 

 twenty-four hours, the corpuscle ap- 

 pears thin and flat, with a very thin 

 rim around the edge, quite box-like. 

 Many corpuscles appearing round 

 and even with transmitted light, appear 

 irregular or slightly crenated with 

 the vertical illuminator. With the 

 latter illuminator the corpuscles ap- 

 pear delightfully clean and distinct, 

 and very accurate contacts with the 

 spider-line can be made. 



The following table was constructed 



