CHAP. II.] 



THE BLOOD. 



77 



occupies from first to last not longer than ten minutes and the mean possible 

 errors amount to 2 or 3 per 100. 



Method of This method is almost exactly similar to that to be 



Hayem and nex t described at length as Dr Gower's. The diluted blood 

 Nachet. j s introduced into a cell of exactly known depth, and the 



number of corpuscles is counted by means of an eye-piece micrometer 

 similar to that used in the method of Malassez. 



Method of Dr Gowers has modified the instrument of MM. Hayem 



Dr Gowers. and Nachet and to it has given the name of the Haema- 

 (The Haema- C y tometer l . 



cytometer.) r^^ following description of his' method is taken from an 



article by Dr Gowers in the Lancet for December 1, 1877 : 



"The Haemacy tometer consists of (1) A small pipette, which, when 

 filled to the mark on its stem, holds exactly 995 cubic millimetres. It is 

 furnished with an indiarubber tube and mouthpiece to facilitate filling 

 and emptying. (2) A capillary tube marked to contain exactly 5 cubic 

 millimetres, with indiarubber tube for filling, &c. (3) A small glass 

 jar in which the dilution is made. (4) A glass stirrer for mixing the blood 



FIG. 14. 



A. Pipette for measuring the diluting solution. 



B. Capillary tube for measuring the blood. 



C. Cell with divisions on the floor, mounted on a slide, to which springs are fixed 

 to secure the cover-glass. 



D. Vessel in which the solution is made. 



E. Spud for mixing the blood and solution. 



F. Guarded spear-pointed needle. 



1 The Haemacytometer is made and sold by Mr Hawksley, Surgical Instrument 

 Maker, 300, Oxford Street, London, W. 



