November, igo6.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



597 



section in alum cochineal, but I have not myself tried 

 this. The alcoholic solutions must not be mixed with 

 the hsematoxylin, which, in Delafield's solution, is a 

 watery and not an alcoholic solution, and borax car- 

 mine is precipitated by strong alcohol. Almost any 

 mounting medium may be used, but those which are 

 used for sections in watery media are perhaps most 

 suitable, such as glycerine jelly or Farrant's solution. 

 Air bubbles will be found to be a nuisance, but these 

 can be largely obviated by soaking in freshly-boiled 

 water prior to mounting, and by carefullv examining 

 the sections under a microscope and working the bub- 

 bles out with a dissecting needle. 



Staining Microscopic Animals and 

 Plants on the Slide. 



The ordinary method of fixino sections, and more 

 especially serial sections, to the slide by means of egg- 

 albumen can be readily adapted to the fixation of micro- 

 scopic animals and plants. The albumen fixative is 

 made as follows: White of egg, 50 cc. ; glycerine, 

 50 cc. ; salicylate of soda, i grm. Shake up well and 

 filter, the last process being a slow one. Take a minute 

 drop of the fixative and place it in the centre of the 

 cover-glass and then smear it evenly so as to form 

 the thinnest possible film. It is important that the 

 slide should be absolutely clean and free from grease. 

 Then place on the surface of the film a drop or two 

 of water containing the organisms and allow the water 

 to evaporate, protected from dust, until the film of 

 fixative alone remains slightly moist. The slide can 

 now be passed bodily through any fixing, dehydrating, 

 staining, or clearing re-agents, and mounted in anv 

 desired way. The method is particularlv useful with 

 lowly forms of animal and plant life, cspeciallv the 

 former. 



The Cathcart-Darlaston Microtome. 



.\mongst inexpeiisi\e microtomes, the Cathcart 

 microtome has long been a favourite. In its simplest 

 form it is made with plain glass-bearing surfaces for 

 u.sc with an ordinary razor nr planing iron, but a later 

 pattern has brass slides, upon which runs a carrier 



for the razor, and by this means more uniform and bet- 

 ter graduated sections can be cut. Mr. Darlaston has 

 just designed a simple, but effective, addition, which al- 

 lows a definite thickness of .section to be cut. The illus- 

 tration shows the general principle. The forks A are 

 attached to the knife carriage, and are provided with 

 slots, so that their distance from one another can be 

 increased or diminished as desired, and held clamped 

 by means of thumb screws. The distance between 

 these forks regulates the number of teeth by which the 

 milled head raising the object to be cut is turned, thus 

 regulating the thickness of the section. By this means 

 any thickness from i/25oth to i/5ooth part of an inch, or 

 even less, can be cut, for the screw turned by the milled 

 head has 40 threads per inch and the head it.self has 

 200 teeth. Beyond the actual cutting of the section, 

 the most important feature is the fact that it is auto- 

 matic in action. The knife carriage is moved forward 

 in the ordinary way, the section cut, and as the carriage 

 is drawn backwards the milled head is turned and the 

 object raised, so that with the next thrust forward of 

 the knife in its carriage, the material has been rai.sed 

 the desired amount and is ready for a fresh .section to 

 be cut. When drawing the carriage backwards, how- 

 ever, it is advisable to slightly tilt it so that the back 

 edge of the razor may clear the section. The auto- 

 matic gear can be at once thrown out of gear when 

 desired, and the milled head then rotated by hand. 

 This microtome is supplied by W. Watson and Sons, 

 with fittings for both imbedding and freezing, at the 

 price of jQ2 5s. 



Quekett Microscopical Club. 



The Hon. Secretary informs me that the arrange- 

 ments for the series of " Demonstrations in Practical 

 Microscopy," mentioned in our October issue, page 

 573, are now complete, and will be given as follows : — 



Friday, November 16, Mr. H. F. .-Xngus, on " .Axial 

 .Substage Illumination with .Artificial Illuminant." 



Friday, December 21, Mr. H. F. .\ngus, on "Dark- 

 ground Illumination." including the means of obtaining 

 a darkground with objectives of high aperture. 



Friday, January 18, 1907, Mr. Chas. I^ Curties, 

 F.R.M..S., on "Polarised and Multi-colour Illumina- 

 tion," and " Various Methods of Recording Observa- 

 tions." 



No demonstration in February on account of .\nnual 

 General Meeting. 



Friday, March 15, Mr. Conrad Beck, F.R.M.S., on 

 " The Illumination of Opaque and Unmounted 

 Objects." 



Friday, .\pril 19, Mr. Conrad Beck, F.R.M.S., on 

 " The Comparison of Objectives," and " Mono- 

 Chromatic Illumination." 



Friday, May 17, Mr. F. W. Wat.son Baker. F.R.M.S., 

 on " Tlie Beginner in Difficulties," a supplementary 

 demonstration which \\ ill also deal with anv questions 

 which may arise in the cour.sc of the preceding ones. 



The demonstrations will be given at 7 p.m., at 20, 

 Hanover Square, W'. Cards of admission to the 

 demonstrations and to the ordinarv meetings mav be 

 obtained from the leading opticians, or the Hon. 

 Secretary, Mr. .\. Farland, ^r, Denmark Street. Wat- 

 ford, Herts. 



[Communkatwn'i and enqiihits on Microscof'ical matters should bt 

 addressed to F. ShilUngton Scales, "Jersey," St. Barnabas Road, 

 Cambridge. Correspondents are requested not to send sfeeimtns to be 

 named.l 



