ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



561 



surrounded by a groove about half the thickness of the slide in depth. 

 Outside this groove are three pointed metal screws equidistant from 

 each other, the elevation of which above the surface of the slide is 

 exactly i- mm. In the centre of the glass block the squares are 

 drawn in which the corpuscles are counted. The sides of these are 

 ■^ mm., and they are arranged in groups of twenty, as shown in 

 Fig. 106 (x 200). 



To facilitate lowering the cover^glass so as to be exactly horizontal, 

 M. Malassez devised the frame (Fig. 105) to the underneath part of 

 which the edges of the cover-glass are attached by a little water or 

 saliva. The frame is supported on two arms attached to one flange of 



Fig. 107. 



a hinge, the other flange being secured to the slide by a clasping 

 screw. The frame with the cover-glass is raised or lowered by the 

 longer of the two arms, and the operation may be quickly performed. 

 A small spring clip keeps the whole down so that there is no danger 

 of the cover being raised or displaced. 



Fig. 108. 



The mixing of the blood is effected in the " Melangeur Potain," 

 shown in Fig. 107, and the whole apparatus, with triangular knife for 

 making incisions, cover-glass, and a bottle of diluting liquid, packs 

 into a small pocket-case 13*5 x 8 X 2-5 cm. (Fig. 108). 



Ser. 2.— Vol. II. 



2 P 



