The Microscope. 315 



aid of a vice, putting in one screw at a time, until the circuit is 

 completed The pressure of the vice holds the steel against the 

 wood until it is fastened by the screw. Before the steel is bent 

 around the wood, firm holes for the screws should be punched 

 where needed with a blunt-faced punch, and be afterwards reamed 

 out. Five screws generally answer. The steel should be laid on a 

 piece of hard wood or block of solder for this purpose. If the spring 

 is too hard to punch a hole through it, take out the temper by heat- 

 ing in a stove and cooling by throwing into a bed of ashes. It will 

 be seen that the thickness of the spring, about one thirty-second of 

 an inch, will be too great to cut the paper clean and sharp; hence I 

 advise filing down one edge, the inner, before the steel is attached 

 to the block. In putting it on, the ends should come close together; 

 if they lap a trifle, they can afterwards be filed away. In shaping 

 the spring around the block, a pair of pliers and a hammer will be 

 of service. For making square shapes, a thinner steel, to be 

 obtained of dealers in machinists' tools, will be found preferable to 

 the clock- spring. 



To cut out the mats, I simply fold a sheet of paper 8 x 10 in 

 sixe until it is four layers in thickness, place it on the steel die, and 

 then, having a piece of mahogany wood, with the end grain in con- 

 tact with the paper, several quick taps with a hammer are given, and 

 the mats are made. 



New Artificial Fluid for Counting Blood Corpuscles. — The 

 Medical News takes the following from the Wiener med. Pr., June 

 10, 1888: At the last session of the Paris Acad^mie des Sciences, 

 Mayet submitted a new artificial fluid for measuring the corpuscular 

 elements of the blood. Four cubic mm. (6^ minims) of blood are 

 mixed with 500 cubic mm. (1| fluid-ounces) of a watery solution of 

 osmic acid, and allowed to stand for three minutes. Then 500 cubic 

 mm. (If fluid-ounces) of a mixture of 45 cubic cm. {1^ fluid-ounces) 

 of pare glycerine, an equal quantity of distilled water, and 17 cubic 

 cm. (4f drachms) of a watery solution of eosin are added. The red 

 corpuscles are colored red by this solution, while the white remain 

 uncolored. By this means the counting is notably facilitated. 



Japan wax, which is advocated as an imbedding material, is 

 obtained from the Rus succedaneum, a tree growing eight or nine 

 meters high. The wax melts at from 5<S|^° to 54|^^ C, and solidifies 

 at 40. 5 « to 46.5°. 



