THE INDIVIDUAL GROUPS OF PROTEINS 475 



(b) With the Thoma-Zeiss H cemocytometer. 



The apparatus (Fig. 57) consists of (i) a glass slide upon which is fastened a 

 square glass cell : a circular disc ruled in squares of ^^ sq. mm. area is cemented 

 to the floor of the cell. The cell is covered with a cover slip. The height 

 of the cover slip from the bottom of the cell is -i mm. A volume of liquid: 



o 



* r . 



0.100mm. 



C, Zeiss 

 Jena. 



FIG. 57. 



occupying -i x ^ or T7 ^ nr cmm. is above each square ; (2) a graduated pipette 

 with a bulb containing a glass bead. These divisions bear an exact ratio to 

 the volume of the blood. 



The second drop of fresh blood from the finger or ear, cleaned with acetone, 

 and obtained by pricking with a lancet, is sucked up in the pipette to the 

 mark '3, *5 or i. The pipette is wiped and diluting fluid (Hayem's fluid 

 = 5 gm. HgCl 2 + 5 gm. Na 2 SO 4 -f i gm. NaCl + 200 c c. H 2 O, coloured 

 with methyl violet) is sucked up to the mark 101 whilst the pipette is continu- 

 ously rotated between the finger and thumb so as to ensure mixing. The 

 pipette is closed with the fingers without removing the rubber tube and the 

 contents are shaken for i minute. Three or four drops are blown out of 

 the pipette and then a minute drop is placed on the centre of the ruled disc.. 

 The cell is covered with the cover slip, avoiding any escape of the liquid into- 

 the portion around the disc. The number of corpuscles in 40 squares is 

 counted. Corpuscles on the top and right side do not belong to the square. 

 The counting should be in the order five left to right, five right to left in next 

 row, five left to right in next row and so on. It is advisable to note the 

 totals for each 5 or 10 squares. 



The dilution of the blood is as the volume of blood taken to the total 

 volume of the mixture, e.g. : 



3/100 'S/ioo i/ioc 



i.e. it is 



100 100 100 



'3 "5 



The volume of the liquid above the squares is ^Vff* 

 Hence the number of corpuscles per cubic millimetre of blood is 



4000 x dilution x total corpuscles counted 

 No. of squares counted 



The error is 5 per cent, when 16 squares are counted, 2 per cent, for 

 and i per cent, for 400. 



