B8 THE AMERlOAK MONTHLY [March, 



and acetic acid is then added until the Hcjuid is on the point of 

 coaguhtting. It is then placed in a copper tube tapering at the 

 bottom, and this tube is inserted in the centrifugal machine and 

 turnetl at the rate of 3,600 revolutions per minute for 15 minutes. 

 The bacilli collect at the narrow end of the tube, together with 

 other sediment and dirt. The liquid is poured off, and the 

 sediment examined microscopicall}'. 



Another, Thorner's method, is this: 20 c. c. of suspected milk 

 are mixed with i c. c. of ^o per cent, potash solution and heated 

 in a bath of boiling water until the fat is saponified, when the 

 solution turns yellowish brown. By this treatment the casein 

 and albumen become soluble in acid. Add 20 cubic c. c of acetic 

 acid, shake the solution, heat on water-bath for 3 minutes, trans- 

 fer to a strong glass tube and turn in the centrifugal machine for 10 

 minutes. The liquid is then poured oft^ and the sediment is 

 washed bv shaking with 30 c. c. hot water, and again turned in 

 the centrifugal machine. The water is poured of!" and the sedi- 

 ment placed upon cover-glasses, which are treated in the ordinary 

 way, staining vvitli hot Neelson solution, decolorizing in 25%" 

 sulphuric acid, and finally staining in methylene-blue. Instead 

 of washing the cover-glasses in sulphuric acid. Thorner simply 

 uses a solution of methylene-blue containing sulphuric acid. — 

 Natiire^ Jan. 12, 1S93. 



To Mount Fish-Scales. — In preparing fish-scales as trans- 

 parent slides for examination by polarized light, or with a black 

 background, they are usually mounted in Canada balsam to ren- 

 der them transparent, but this means of mounting gives a dull 

 and muddy image ; their appearance is greatly improved by 

 mounting them in a mixture, half alcohol and half water, the 

 image is orighter and clearer, and the colors with polarized light 

 and a selenite plate much more brilliant. 



By using a Herapathite film mounted as the analyzer the 

 image is very much brighter, and the colors stronger when using 

 the selenite than with a Nicol eyepiece ; but without the selenite 

 plate the field gives onl}' a dull brown color, instead of being a 

 deep black, as with two Nicols. 



It is very desirable that the scales should be perfectly clean and 

 free from the slime that adheres so obstinatel}', especially in such 

 scales as have strong spines, as the sole, perch, etc. The scales, 

 when possible, should be gently detached from the fresh skin, be- 

 ing careful not to break oft" any of the spines, and cleaned by 

 steeping them in warm water and gently brushing oft' the mucus 

 with a camel's-hair brush ; but if this does not succeed in perfectly 

 cleaning them they should be digested for some hours with pep- 

 sin, when they can be thoroughly cleaned. As it is difficult to 

 find a means of fixing the scales to the slide when mounting in 

 spirit, the cells should be made in the turn-table with asphalte 

 to such a depth that the cover-glass when mounted will hold 

 them with a slight pressure. — No Sig. Paris. 



