ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 521 



Beautiful slides have been prepared upon small circles of speculum 

 metal, in which the lines are protected by nickel plating. The lines 

 are very sharp under the nickel. With a vertical illuminator and 

 very high powers this form is recommended. 



Yeast Counting Apparatus. — Herren Klonne and Miiller supply 

 an apparatus for use by brewers in counting the number of cells in 

 yeast and thus judging of its quality. It is practically identical 

 with the blood-corpuscle counters, and consists of a slide with a cell 

 of definite capacity, a reticular micrometer, and a pipette. 



Metal Micrometers.* — Mr. M. D. Ewell calls attention to the 

 fact of the very great superiority of metal micrometers over glass. 

 To pay nothing of their greater durability, in point of clearness and 

 sharpness of outline there is no comparison whatever between the two. 

 With a high power the edges of lines ruled upon glass appear rough 

 and uneven ; but the author has never yet been able to find a power 

 high enough to produce an effect upon a speculum metal centimetre 

 ruled to 1/100 mm,, though he has examined it with a Zeiss 1/18, 

 Bausch and Lomb amplifier, and 1/2 in. solid eye-piece, with the draw- 

 tube drawn out to its greatest length. 



Circulation Plate for Frogs, &ct — Prof. S. H. Gage says that an 

 excellent circulation board for Necturus and frogs may be prepared 

 by boring a hole about 2 cm. in diameter in a pine board 8 x 30 cm. 

 and 15 mm. thick. The hole should be about 5 cm. from one end 

 and near one side. A perforated cork or hollow cylinder of wood 

 should be fitted to this hole. Over the top of the perforated cork 

 should be placed a very thick cover-glass or a piece of thin glass 

 slide, and sealed with sealing-wax ; finally the whole board should be 

 covered with woollen cloth or cotton flannel. The perforated cork 

 should be capable of being moved so that it will stand a centimetre 

 above the surface of the board if desired. 



Malassez's Haemochromometer.l— Dr. L. Malassez's instrument 

 serves to estimate the intensity of the colour of blood by placing in a 

 wedge-shaped trough a solution of the blood to be examined and then 

 determining at what point of the wedge the solution reproduces the 

 tint of a fixed standard. This point will, of course, be so much the 

 nearer to the apex of the wedge as the blood examined is richer in 

 haemoglobin. Dr. Malassez's apparatus is therefore the inverse of 

 the old one. 



A small metal plate (fig. 105) forms a screen having in its centre 

 two circular holes. Behind one of these is placed the coloured 

 standard and behind the other the vessel for the solution of blood. The 

 coloured standard is formed by a small glass trough inclosing a solu- 

 tion of picrocarmine, which reproduces exactly the colour of a solution 

 of 1 in 100 of blood containing 6 per cent, of haemoglobin. The 

 trough is mounted in a brass box, and fixed in a metal ring. The 



* The Microscope, vi. (1886) p. 63. 

 t Notes on Histological Methods, 1885-6, p. 10. 

 X Arch, de Physiol., 1882. 

 Ser. 2.— Vol. VI. 2 M 



