SCIENCE-GOSSIP. 



151 



CONDUCTED BY J. H. COOKE, F.L.S., F.G.S. 



To whom Notes, Articles and material relating to Microscopy, 

 and intended for Science-Gossip, are, in the first instance, 

 to be sent, addressed "/. H. Cooke, Edlestone, Battenhall 

 Road, Worcester." 



Mounting Lichens. — In the current number of 

 the "Journal of Applied Microscopy," Mr. G. H. 

 French gives the following method for the mount- 

 ing of lichens. First the lichen is put into ninety- 

 five per cent, alcohol for twenty-four hours, then 

 into thin celloidin for another twenty-four hours. 

 After this the specimens are imbedded in thick 

 celloidin which is hardened in seventy per cent, 

 alcohol for twenty-four hours and then cut. 

 Cryptogam sections should be stained with borax 

 carmine, as it gives better results than any other 

 stain. 



Imbedding Lichens. — For many lichens a 

 harder grade of paraffin must be used than for 

 most vegetable structures. A mixture of hard and 

 soft paraffin, which melts at about 60° C, is 

 recommended. Clear the specimens in pure xylol, 

 and to this add small pieces of paraffin, keeping 

 the dish warm at the same time both to increase 

 the solvent power of the xylol and also gradually 

 and finally to evaporate it all. By this means the 

 material is slowly warmed and penetrated with 

 paraffin. After remaining in melted paraffin abso- 

 lutely free from xylol for three hours the subject 

 may be imbedded. The sections should be 

 very thin, and before cutting the block should be 

 chilled to somewhat below 20° C. The microtome 

 knife must be very hard, sharp and rigid. Stain 

 by any of the usual methods. 



Photo-Micrography of Opaque Objects. — 

 At a recent meeting of the Botanical Society of 

 Edinburgh, Mr. R. A. Robertson, M.A., B.Sc, 

 read a paper on " A New Method for the Photo- 

 micrography of Opaque Stem Sections." One diffi- 

 culty in making photo-micrographs from recent or 

 fossil stem sections is the trouble of getting a 

 sufficiently large section to bring out diagnostic 

 features. Another is, that it is a difficult process 

 to cut and grind and polish large sections of fossils 

 for photography by transmitted light. Neither 

 can one always get permission to make sections of 

 valuable museum specimens of recent and fossil 

 woods. Mr. Robertson has found that by directly 

 photographing the surface by means of a micro- 

 photographic apparatus, excellent pictures, giving 

 all necessary histological details of the tissues can 

 readily be obtained. The recent wood surfaces 

 are planed with a steel plane, and if at all rough 

 the surface is wetted. Very careful focussing is 

 necessary, so as to get equal illumination. An 

 opaque focussing plate should be used for rough 

 adjustment, but the final focussing must be done 

 with a clear glass plate. The illumination was by 

 means of a magnesium ribbon fed through a fixed 

 tube and placed at an angle of 45° and a distance 

 of ten or twelve inches from the surface to be 

 photographed. An exposure of about forty seconds 

 with Ilford plates gave the best results. 



Bacteria in Ground Water. — The readiness 

 with which bacteria may be conveyed to wells in 

 sub-surface water has been shown in some experi- 

 ments made on the Rhine near Strasburg by Prof. 

 E. Pfuhl. Two kinds of bacteria, neither occurring 

 in the Rhine, were placed in a shallow pit nearly full 

 of water and in one hour one species had passed 

 through twenty-four feet of gravel to a second pit, 

 the other species appearing in the second pit within 

 two hours. 



Quick Method of Preparing Sections. — It is 

 often desirable to prepare sections of soft tissues 

 in a very short time. To those who are familiar 

 with the collodion method the following suggestions 

 by Mr. M. B. Thomas in the "Journal of Applied 

 Microscopy " will be helpful. Place the tissue at 

 night in forty per cent, alcohol in the dehydrating 

 apparatus. Remove it at 7.30 the next morning. 

 Leave until 10 o'clock in two per cent, collodion. 

 Then place in five per cent, collodion until 11.45. 

 Arrange on the cork and place in eighty per cent, 

 alcohol. The material will be ready to section at 

 1.30. A total of eighteen to nineteen hours covers 

 the whole operation. 



Nematodes for Microtome Sections. — The 

 following methods of preparing nematodes for 

 sectioning with the microtome has been used by 

 Dr. Kaiser with much success. The main diffi- 

 culty to be overcome is the curling up while being 

 killed. To prevent this place the worm on a slide 

 with a few drops of water. Over it place another 

 slide and move it slowly to and fro. This move- 

 ment causes the worm to straighten. As soon as 

 the nematode assumes the desired position the 

 fixing liquid is pipetted between the slides, the 

 motion of the upper slide being continued until 

 the worm is dead. By this method one can obtain 

 a specimen which is perfectly straight and round. 



Sectioning Bolitic Grains. — Lay a glass slip 

 on a metal plate and place it over a spirit lamp. 

 Soften a drop of nearly dried balsam upon it with 

 heat, and lay a small plate of mica on it so that 

 it will become cemented to the glass. Upon the 

 mica surface imbed in balsam and arrange the 

 small objects of which sections are desired. When 

 the balsam is cold and firm the glass is used as a 

 handle by which to hold the objects whilst 

 grinding. A flat surface may be given them as 

 they lie in the balsam, by rubbing with a hone. 

 Heat the glass to release the mica by softening the 

 lower film of balsam, lift the mica with forceps 

 and turn it over on another glass which has been 

 provided with balsam. The ground glass is now 

 downwards, and the other side may be ground 

 as desired. 



Longevity of Germs. — Some remarkable 

 observations on the longevity of germs in dust 

 have been recorded by Dr. Miquel, a French 

 biologist and microscopist. In 1881 some earth 

 was taken from a depth of ten inches in Montsouris 

 Park, dried for two days at 30° C, and then put 

 away in a dark corner of the laboratory, first being 

 hermetically sealed in tubes. On recently opening 

 the tubes, after sixteen years, it was found that the 

 dust still contained 3,500,000 microbes per gramme, 

 the original number in the soil having been but 

 6,500,000 per gramme, which the drying reduced to 

 rather less than 4,000,000. From the surviving 

 bacteria the tetanus microbe was isolated, and 

 so wonderful was its vitality that its action was 

 effectual in guinea pigs after an incubation period 

 of two days. 



