HARDWICKE'S SCIENCE-GOSSIP. 



There are several text-books on the microscope, 

 and on microscopical technology ; most of these 

 works are bulky and expensive, and even if they 

 are within the easy reach of many, they are too 

 formidable to be "read, marked, learned, and 

 inwardly digested." Space will not i^ermit me to 

 criticise these stupendous volumes, more than to 

 state, that they do not contain what I am about to 

 explain. But there are other smaller works, inex- 

 pensive, and full of practical hints ; they are greedily 

 read by every tyro microscopist, and to them do we 

 owe the main impetus which has of late been given 

 to popular microscopical research, by bringing the 

 subject within the easy grasp of those who study in 

 their leisure to derive pleasure. In these little books 

 the harassing details of their bulkier brethren are 

 avoided, and only practical items are noted. As I 

 must not prolong this paper by criticising the 

 directions given in Mr. Marsh's little volume, or in 

 Dr. Heneage Gibbes' practical work, I shall merely 

 refer the reader to one or two things in those 

 treatises, concerning the difficulties of mounting 

 objects for the microscope in Canada balsam, and 

 then describe a method which, if followed in its 

 integrity, will dispense with all those difficulties and 

 a great deal of unnecessary trouble as well. 



Thus, Dr. Gibbes, in speaking of mounting large 

 sections,* finds that the cover glass on to which he 

 has succeeded in transferring the section is smeared 

 all over the top with clove oil, and has thus to 

 remain for some time ere it can be cleansed for 

 examination. Mr. Marsh devotes some pagesf to the 

 description of apparatus for drying slides after they 

 have been mounted, and in a footnote % gives a 

 "wrinkle,"' which he ascribes to Mr. Kay, for the 

 prevention of air bubbles in slides mounted in viscous 

 balsam, with a few remarks to advise the use of 

 viscous balsam for thick tissues, because the 

 prepared mobile balsam is apt to evaporate and leave 

 vacuoles behind. I have referred to these two handy 

 volumes because they are so well known, and I am 

 aware that the plans inculcated in them are those in 

 general use, and in almost every text-book, whilst 

 very few persons know how to mount objects in 

 Canada balsam and avoid the defects which have 

 been alluded to above. That all such defects can 

 most readily be obviated, even by the most inex- 

 perienced worker, it sliall be my present endeavour 

 to show. 



As success in mounting olijects depends upon a 

 certain amount, the larger the better, of methodicity 

 and cleanliness, I shall preface these remarks with a 

 few maxims, and describe the mounting process 

 progressively by means of an example. 



* " Practical Histology and Pathology," by Heneage Gibbes, 

 M.D., and ed., H. K. Lewis, Gower Street, London, 1883, 

 PP- 54- 



t " Microscopical Section Cutting," by Sylvester Marsh, 

 L.R.C.P.E., 2nd ed., J. & A. Churchill, New Burlington 

 Street, London, iSS.!, pp. 115-iig.* 



+ Op. cit., p. 109. 



I. Before commencing your work always see that 

 your table, windows, and in fact everything in the 

 room, are quite clean and free from dust. 



II. See that your microscope, spirit lamp or Bunsen 

 burner, bottle of balsam, dipping-rod, forceps, knife, 

 lifter, etc., are all in good condition, and arranged on 

 the table in the most convenient positions. 



III. Have ready by your side a box containing a 

 sufficiency of cleaned cover glasses and glass slips, so 

 as to avoid having to clean anything whilst at work. 



I shall now describe the way in which any thin 

 section, however large and prone to curl up, may be 

 successfully mounted. 



1st. Remove the section to a dish* containing some 

 clean filtered methylated spirit, f and allow it to 

 remain in this for about an hour, so as to thoroughly 

 dehydrate it. The fastidious worker may re-transfer 

 it to absolute alcohol for another hour, but this is 

 quite unnecessary. 



2nd. Pour a little oil of cloves into another palette. 

 Drain as much spirit as possible off the section, and 

 allow it to float on to the surface of the oil. In the 

 course of a short time, which varies from the fraction 

 of a minute to a few minutes with the nature of the 

 section, the specimen will sink to the bottom of the 

 oil, and thus show that it has been thoroughly per- 

 meated ; it may now be removed, but not necessarily, 

 as prolonged soaking in the clove oil will not damage 

 it much. Care must be taken, however, to keep the 

 palette covered, to prevent the admission of foreign 

 particles, of dust, hairs, &c. 



3rd. Procure a clean glass slip, breathe on it 

 gently, and to the surface of condensed vapour apply 

 a clean cover glass ; the latter will be found to adhere 

 to the glass slip sufficiently to prevent its falling off 

 during the subsequent processes. On to the centre of 

 the cover glass place a drop of benzoled balsam ; lay 

 the section in this drop, and examine it under a 

 low power of the microscope (two-inch objective with 

 A eye-piece). If any foreign particles have crept in 

 they must be removed with a needle. ij: Air-bubbles 

 may be disregarded. 



Should a very large section be floated on to the 

 cover glass from the oil of cloves, drain off the super- 

 fluous oil and place the cover on a clean glass slip 

 with the section uppermost and exposed, and cover 

 the section with benzoled balsam. Care must be 



* A useful kind of dish may be procured from any artists' 

 colourman in the form of a circular china palette about four 

 inches in diameter. The palettes are usually sold in nests of 

 six, and may be used as staining and clearing troughs, and for 

 a variety of other purposes. 



f Methylated spirit should be perfectly clear and colourless. 

 It should register 63 (or at least 59) above proof on the alco- 

 holometer. 



X It is of the utmost importance in the production of neatly- 

 mounted sides, that the worker should be able to use a needle 

 to remove dust particles from the preparation under a compound 

 microscope. Perseverance for a couple of hours at a slide full 

 of such particles will enable any ordinarily neat-handed person 

 to succeed in this. A simple microscope may be used by those 

 who are not endowed with a small stock of patience ; but I 

 recommend the mastery of this feat with the compound micro- 

 scope, as experience has proved it to be the most satisfactory 

 method. 



