July, 1906 ] 



KNOWLEDGE & SCIENTIFIC NEWS. 



493 



At a recent meeting of the Royal Microscopical 

 Society, Dr. Hebb read the following further com- 

 munication from Mr. Nelson, which will interest many 

 microscopists : — " It may interest you to hear that 

 the flagella of the tubercle bacillus can be seen with a 

 dry lens. The apochromatic 4 m.m. (long tube), by 

 Zeiss, and the 7a (short tube), by Leitz, both will 

 demonstrate the flagellum. There is nothing of 

 particular interest in this of itself, but there is one point 

 worth noting, which is, that it is only the bacilli stained 

 with fuchsin that will shine on a dark ground ; other 

 objects in the field, such as nuclei stained blue, hardly 

 show up at all upon a dark ground. Therefore, if the 

 flagellum was, as has been said, some other object 

 stained blue and lying fortuitously against the bacillus, 

 it never would have been seen upon a dark ground. 

 The image is necessarily a difficult one, even shining 

 as it does with the fuchsin in it, but unless it was an 

 integral part of the bacillus, and took the stain with 

 it, it would be perfectly invisible." 



In reference to the remarks made above as to the 

 beaded appearance of tubercle bacillus, Mr. Nelson 

 calls attention to the fact that improved methods of 

 staining show the unit cell to be square ended, the 

 apparent distance between one cell and the next is 

 much reduced, and the whole bacillus looks something 

 like a jointed bamboo; the resolution of these joints 

 has become proportionately more diflficult, and can no 

 longer be performed by quite low powers. 



As branching forms of this organism have been seen 

 by other observers, as well as clubbed and swollen 

 shapes, and gland-like clusters in experimentally af- 

 fected animals, the evidence seems tO' be accumulating 

 that Bacillus tiihcrciilosis should not be included amongst 

 the monomorphous bacteria, and does not represent 

 a single bacillus, but belongs rather to fungi of the 

 nature of actinomyees, and that the name " tubercle 

 fungus," would be in the meantime preferable. 



New Form of "Erlich" Eyepiece. 



Messrs. R. and J. Beck, Ltd., have brought out a 

 new form of " Erlich " eyepiece for counting blood 

 corpuscles. It is of the standard students' size (R.M.S. 

 No. I gauge), and is provided with a square aperture 

 which is adjustable by means of an external and 

 graduated wheel, and can be varied from i mm. to 

 8 mm., so that it can be instantly set to the most con- 

 venient size. The actual area to which the size in use 

 corresponds when used with any particular object-glass 

 is ascertained by slipping a stage-micrometer on the 

 stage of the microscope. 



New Oil Immersion Objective. 



Messrs. A. E. .Stnley :in(l ("ci., ha\<' soni nu', lor 

 examination, a new 1-161I1 inch honuigeneou.s immer- 

 sion objective, with a numerical aperture of 1-3, made 

 by the Bausch and Lomb Optical Co. The use of a 



lens of this magnification is limited, as it is an axiom 

 of modern microscopy, that resolution is dependent 

 upon aperture and not on mere empty magnification, 

 but given a certain aperture, and consequently a pro- 

 portionate resolving power — that is, for example, an 

 ability tO' resolve a certain number of lines to the 

 inch — it still is necessary for these lines to be magni- 

 fied sufficiently to enable the human eye to distin- 

 guish them. It is here that the personal factors come 

 in. Some observers have keener vision than others, 

 either by nature or by training, and I have myself 

 lound that the average observer needs an object to be 

 magnified to a point possibly beyond that of best defini- 

 tion if he istoEeeittohissatisfaction. But most objectives 

 will not stand really high eye-piece magnification, and 

 the higher the power of the objective, the less will they 

 bear a high eye-piece. It is therefore sometimes ad- 

 vantageous toi obtain a given magnification bv in^ 

 creasing the power of the objective, and contenting 

 oneself with a lower eye-piece, and many workers find 

 an objective of moderately increased power, such as 

 a i-i6th inch, easier to work with on difhcult ob- 

 jects than a i-i2th inch of the same aperture, and 

 ec|ual theoretical resolving power. Of the lens under 

 notice, I can speak highly. Its definition is excellent, 

 and its working distance ample. I have tested it on 

 some difficult spirilla, as well as in more theoretical 

 ways, and was much pleased with its performance. 



Microscopical Material. 



By the kindness of Mr. Edwin R. Gill, of Poole, 

 I am able to offer to such of my readers as care to 

 apply for it some specimens of Droscra (Sun-dew). 

 -Vpphcations must be accompanied by a stamped and 

 addressed envelope, and by the coupon to be found in 

 the advertisement columns of this issue of "Know- 

 ledge." 



Notes and Queries. 



FloatiiKis of Foiaminifera. — .Mr. F. Mockler, of Bath, 

 will be glad if any reader can tell him where he can get 

 some floatings of Foraminifera, which will give him some 

 Xodosaria and Dcntalina. 



Staininq Yeast Nuclei (B. C. S., Bradford). — Veast 

 nuclei are very difficult to stain, and to see when stained. 

 They must be first fixed with weak Flemming's solution, 

 and then stained with such nuclei stains as saffronin, 

 orange G, or gentian violet. The first of these stains is 

 perhaps the best, though it takes rather longer than the 

 others. Before staining, the fixing solution must be washed 

 out by irrigation methods, and after staining h-rigated in a 

 similar way with alcohol and oil of cloves. 



Volcanic Dust from Mont I'cice Eruption. — Mr. W. A. 

 Rogerson, of Longsight, writes in reply to the enquiry of 

 the Rev. \V. Hamilton Gordon : " I have a little volcanic 

 dust from Vesuvius, collected on a steamship, in the Bay 

 of Naples, on the deck of which it lay an inch deep. A little 

 of this dust was mixed with benzole, and well shaken upon 

 settling. A slide was arranged with a drop of benzole 

 solution of Canada balsam, a little of the dust from the 

 benzole washing was then put into this drop of Canada 

 balsam and well stirred with a needle ; a cover glass, with 

 the lower surface smeared with Canada balsam was then 

 lowered on the dust, and the whole slide left to dry on the 

 liven. The mounted slide should be examined with 

 polarized light, when the particles of contained silica show 

 up very clearly." 



[CommiiniaitioHS and Enquirits on Micrescopital matters shoidd be 

 aJdrcised to F. Shillington Scalts, "Jersey," St. Barnabas Road, 

 Cambridge] 



