THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



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



All commu7iications for this Joiinial, whelhcr relating to biesiness or to editorial 

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

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



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 by International Postal Order for $1.13 per attftum, or they may be sent to Messrs. 

 Triibner &^ Co., j/ Ludgate Hill, London, or to Mr. IV. P. Collins, i^j Great 

 Portland street, London, accompaiiied by the yearly price of five shillings. 



Histological Technique of the Blood. 



By GEORGE C. FREEBORN, M. D., 



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



[ Cant i7iHcd 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 11 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 i 

 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 peri'ectlv 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 cential 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 quicklv 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 op 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 canulae. 



Copyright, 1889, by C. W. Smiley. 



