116 SUMMARY OF CUKRENT RESEARCHES RELATING TO 



pulled or it will break. It is better, perhaps, to use glass rod for this 

 purpose, as* it cannot enclose any air and form bubbles. For mounting, 

 two short pieces of the thread are fixed parallel to each other upon the 

 sHp with a minute quantity of gum, thus forming a support for the 

 cover-glass. There is another purpose for w^hich these glass threads 

 may be used, viz. the picking up and transferring of diatoms. They 

 have been strongly recommended for this by Professor Hamilton Smith. 

 A little practice will enable anyone to prepare threads of almost any 

 required fineness or length. 



C6; Miscellaneous.' 



New Method of Counting Leucocytes.* — The advantage of the 

 method here described, says H. A. P. Hill, is that a total and differential 

 count may be done simultaneously, the whole process taking about ten 

 minutes or less. The only apparatus needed besides the usual Thoma 

 pipette and slide is a small cylindrical tube graduated and corked. The 

 tube of a Haldane's hgemoglobinometer cut down to the level of the 

 120 mark is very convenient. Liquor potassse will clean it after use. 

 The diluent must be made up at the time. Its composition is : distilled 

 water, 12 parts ; acetone, 3 parts ; methyl-alcohol, 1 part; and Wright's 

 modification of Leishman's stain, 4 parts. 



This reagent is used as the diluent for the blood in any dilutions 

 from 1 in 200 to 1 in 10. The red cells become almost invisible, the 

 leucocytes stain just as they do in a film, and can be distinguished with- 

 out the least difficulty. A dilution of 1 in 100 will give some 80 cells 

 on the big square of a Thoma-Zappert slide, which is quite a large 

 enough number to give an accurate total count, and there is no difficulty 

 in finding 300 cells in other parts of the field for the differential. In 

 .marked leucopenia a 1 in 10 dilution enables one to find as many cells 

 as are needed in a few minutes. Three precautions must be observed : 

 1. The Wright's stain must be filtered ; best at the time of making it 

 up. 2. The mixture must be well shaken. 3. The various operations 

 of mixing and putting the dro]3 on the slide must be done with prompt- 

 ness : the drop must be covered as quickly as possible, as the cells settle 

 rapidly and the acetone evaporates readily. 



Metallography, etc. 



Bearing Metals.j — E. Heyn and 0. Bauer have made an extensive 

 series of tests, including determinations of cooling curves and micro- 

 scopical examination, upon white bearing metals (tin-antimony-copper 

 alloys) and bronzes containing about 8-i p.c. copper and 16 p.c. tin. 

 The structure of the rapidly cooled alloys was found to be finer than that 

 of the slowly cooled alloys, and as the mechanical properties are con- 

 siderably affected by the rate of cooling the microstructure is a useful 

 indication of the wearing quahties of a bearing. A high casting tem- 

 perature tends to produce a coarse structure. The effect of the addition 



♦ Lancet (1912) i. p. 20. 



t Stabl und Eisen, xxxi. (1911) pp. 509-12, 141G-22 (31 figs.). 



