Journal of Applied Microscopy. 



133 



Toyson's Fluid (as given by Kahlden). 

 — Methyl violet 5 B, 0.025 grams; neut- 

 ral glycerin, 30.0 cc. ; distilled water, 

 80.0 cc. 



Mix methyl violet in glycerin and the 

 distilled water and to this solution add: 

 sodium chloride (C. P.), 1.0 gram; sod- 

 ium sulphate (C. P.), 8.0 grams; distilled 

 water, 80.0 cc. 



Filter, and the solution will be ready 

 for use. The white blood cells are 

 stained violet, and may thus be counted 

 with the red. 



The diluting fluid contained in the cap- 

 illary tube is then blown out, and a 

 small drop of the diluted blood is placed 

 on the center of the small glass disc. 

 This small disc is surrounded by a ring 

 of glass, cemented to the slide. The 

 glass ring is 0.1 mm. thicker than the 

 glass disc. 



When this small moist chamber is 

 covered with a thick cover-glass, we 

 have a layer of blood 0.1 mm. deep be- 

 tween the disc and the cover-glass. On 

 the upper surface of the small glass 

 disc (on which the drop of diluted blood 

 was placed) there are marked off four 

 hundred small squares. 



The sides of the small squares are one- 

 twentieth of a millimeter long. 



It will be seen that the layer of blood 

 over each of the squares would have a 

 cubic contents of 



^OT of a c. m. m. (j',, X 55 X I's = jijVo)- 



The haemacytometer slide is now placed 

 on the stage of the microscope, where it 

 should remain undisturbed for several 

 minutes before counting. The red blood 

 cells in twenty-five to fifty squares are 

 then counted. To ascertain the number 

 of red cells in a cubic millimeter, the 

 following formula may be useful: 



In case it is desired to count only the 

 white blood corpuscles, a one-third per 

 cent, solution of glacial acetic acid is 

 used for diluting the blood. This solution 

 bleaches the red cells, and brings out 

 clearly the white corpuscles. 



The blood is diluted only ten times, us- 

 ing for this purpose the Thoma-Zeiss 

 pipette for counting white corpuscles. 

 The formula then reads as follows: 



4000 X d (10) X n 



The number of 

 white blood cor- 

 puscles counted 



n (number of squares counted). 



The number 



of white 



= blood cells 



found in 



cubic 

 millimeter. 



Or; multiply the average number of 

 white corpuscles in each square by 

 40,000. 



METHODS FOR OBTAINING, FIXING, 

 STAINING BLOOD PREPARATIONS. 



AND 



In order to be able to examine micros- 

 copically blood preparations it is neces- 

 sary to have the blood spread in a very 

 thin layer, and in such a way that such 

 preparations may be readily fixed and 

 stained. This may be done in several 

 ways. The method here given is es- 

 sentially that suggested by Ehrlich, to 

 whom we owe so much of the technique 

 in this field and so many observations 

 on the structure of the blood in its 

 normal and pathological state. 



The blood is best spread on cover- 

 glasses; a convenient size is a No. 1, 

 three-fourth inch square cover-glass. 

 The size is not so essential, but it is 

 necessary that they be very thin. 



Before using, the cover-glasses should 

 be thoroughly cleaned. This is best done 

 by washing them in sulphuric acid, rins- 

 ing them in water, washing them in 



(Each cube of blood counted'j ( The dilution of ~| [The number) 



4000-( has a cubical contents of vx d-; the blood, which vx n^ of red cells > 



i T5bB c. m. m. j ( would be 100 j ( counted j 



n sq (the number of squares counted) 



The number of red 



blood cells in 



1 c. m. m. 



Or, ascertain the average of the red 

 blood cells in the squares counted, and 

 multiply this number by 400,000. 



Fig. 1. Thoma-Zeiss haemacytometer: a, 

 slide used in counting blood cells; b, same 

 in section; c, pipette used in diluting blood 

 when counting the red blood cells. 



strong acetic acid, again washing thor- 

 oughly in water, and wiping them from 

 alcohol, with a soft, clean cloth. Cover- 

 glasses thus cleaned may be kept on 

 hand ready for use. 



The steps fur obtaining '"blood- 

 spreads' ' are as follows: The blood may 

 be obtained from a finger, the lobe of the 

 ear, or in infants from the large toe. 

 The part should be cleaned by washing, 

 and it is well to wipe it with a cloth dip- 

 ped in alcohol or alcohol and ether. Spe- 

 cial instruments have been devised for 

 incising the skin to cause the blood to 

 flow. I have used, for some time, an 

 ordinary steel pen, from which one of 

 the prongs has been broken, for this pur- 

 pose. This little instrument is readily 



