THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Vol. X. NOVEMBER, 1889. No. 11. 



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 matters, and all books, pamphlets, exchanges, etc., should be addressed to Ameri- 

 can Monthly Microscopical Journal, Box 6jo, Washington, D. C. 



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Histological Technique of the Blood. 



By GEORGE C. FREEBORN, M. D., 



INSTRUCTOR IN NORMAL HISTOLOGY IN THE COLLEGE OF PHYSICIANS AND SURGEONS, N. Y. 



[Continued from page 222.~\ 



Thoma's blood-cell counter, Fig. 5, consists of a glass slide on the 

 centre of which is cemented a square glass plate, P, having a circular 

 opening n millimetres in diameter. In the centre of this chamber a 

 circular glass plate, c, is cemented to the slide. This plate has a diam- 

 eter of 5 millimetres, and on its free surface is engraved a grating 1 

 millimetre square, which is divided into 400 equal squares, Fig. 6. 

 These squares are, by an additional system of double lines, divided into 

 25 groups of 16 squares each. The surface of the plate, P, is ground 

 down so that the distance between the upper surface of c and the under 

 surface of a cover-glass placed on P shall be exactly i-ioth of a milli- 

 metre. The cover-glass should be ground perfectly flat, and should be 

 about 0.35 mm. thick. 



A small drop of the diluted blood from the mixer is placed in the 

 middle of the plate, c, (Fig. 6), and quickly covered. The drop 

 should be of such a size that after being covered its edges will come to 

 the edge of the central plate. The edge of the cover-glass is leaned 

 against the chamber wall and slowly lowered until it comes in contact 

 with the drop of blood, then it is allowed to drop quickly and is 

 pressed gently on the walls of the chamber. The cover-glass is only 

 to be handled with forceps. The preparation is now allowed to rest 

 for a few moments so that the blood-cells can settle, and is then placed 

 on the microscope and examined with a power of 30 to 70 to see — 



Explanation of Plate. 

 Fig. 5. Thoma's blood-cell counter. Fig. 7. Thoma's Frog-plates. 



Fig. 6. Field of Thoma's blood-cell counter. Fig. 8. Inflation canula;. 



Copyright, 1889, by C. W. Smiley. 



