46 



KNOWLEDGE & SCIENTIFIC NEWS. 



[February, 1907. 



Conducted by F. Shillington Scales, u.a., f.r.m.s. 



Royal Microscopical Society. 



DlxKMHKK iq, Dr. 1). II. Scott, l'M\..S., l>i(.-si(l(.'iii, in 

 the chair. Mr. C L. dirties pro.v.'iitccl to the .Society 

 :i dissectiiii^ .stanil, made by the htto l.atiiinr 

 Chirke, C.K., and a li\c-box. Mr. Conrad Hock ex- 

 hibited a new form of hand demon.stralion microscope 

 for low-power objecl.s for use in clas.ses. .Sonie slide.s 

 .selected from the collection presented to the Society 1)\ 

 Mr. Jas. Hilton, were also exhibited. Mr. S. Rogers 

 re.'id a paper on " Microscopic Study of Strain in 

 N'etaLs," which showed the nature of the fatifjuc of 

 steels under alternating strcs.scs of a certain magnitude. 

 He finds that the nature of the effects in the ferrite of 

 steels is different from that in soft iron, and the effects 

 in pearlite depend upon the type of pearlite. It might 

 be expected that incipient cracks would tend to select 

 a cour.se largely through ferrite, but important re:isons 

 show that caution should be exerci.sed in accepting thi.s 

 hypothesis, and much experimental work confirmed the 

 fact that the .selection, though marked, is by nO' means 

 exclusi\e. An important difference exists between 

 ;;tcels rolled or annealed below about 750° C, and those 

 anneak-d at higher temi>eratures, i.e., more or less 

 overheated. In the former, the outcrop of surfaces 

 upon which slip has repeatedly occurred are very 

 numerous, short and crooked, and the surface parallel 

 to the direction of stress becomes ruffled. In the latter 

 type, the outcrops are fewer, less crooked, and longer, 

 and the surface is practically unruffled'. A relation is 

 found to exist between lines which are found upon 

 statically strained pieces, and this leads to the theory 

 that specimens of the "normal " group endure fatigue 

 better than " overheated " specimens, because the per- 

 manent and injurious micro.scopic strains are more 

 minutely sub-divided and uniformly distributed in the 

 former than in the latter. It is conclusively shown that 

 there is a stage in the life of a piece of steel enduring 

 fatig^ue after which, though it is far short of final rui> 

 ture, annealing is futile, if not actuallv harmful. 

 Pieces in this stage, if heated to 250" C, or higher, and 

 then fatigued to rupture, show heat tint-marks on the 

 ultimate fracture, w hich map out the portion of fracture 

 which was sufficiently open at the time of heating for 

 air to enter. 



Quekett Microscopical Club. 

 December 21. Mr. W. R. Travi^s fxhibited and 

 described an expanding central stop for dark ground 

 illumination. Mr. A. A. C. Eliot Merlin, F.R.M.S., 

 communicated a paper on " New Diatom Structure." 

 This dealt chiefly with the recent resolution of " veiled " 

 m.-irkings on some thre^e species of Mclosira, and new 

 .';econdary markings in species of A'avia//c2, H ralodncHs. 

 Aiilodisais, etc. The author had also sent for exhibition 

 two. dark-ground photographs of Triceratmm nova 

 Zcalandica, x 490, taken with a Zeiss 16 mm. apoch- 

 romat, N..'\., 0.35, and a Powell 26 projection eyepiece. 

 The focus in both ca.ses was adjusted on the image of 

 the apochromatic substage condenser stop, formed in 



the central areolations, and the single bar arm of the 

 central stop was well seen in many areolations of both 

 specimens. 



The meeting was preceded by a drmonstralion on 

 " Dark Ciround Illumination," by Mr. II. V . .Angus. It 

 was stated that to .secure the best results, the nunn'rical 

 apertures ol objeclixe, conden.ser, and stop, should lia\e 

 the ratio respectively of i, i, :md i, e.g., if the ol)jecli\e 

 has N..\. 0.33, the v.alue of the central stop should In- 

 0.50, and the conden.ser, N..\. i.o. Methcxls of deter- 

 mining the N..\. \aliie of the conden.ser and of the stop 

 ret|uirjd were given, and the rules laid down were illus- 

 trated by a number of specially arranged microscopes. 

 Collecting- and Studying- Flustrclla 

 Hispida. 



In the "Quarterly Journal of Microscopical Science " 

 R. M. Pace gives a method of study of the larval 

 development of Flustrclla liispii/a which may be of ser- 

 \ ice in other directions. The material was collected on 

 the South Coast, being found abundantly between tide- 

 marks on tiicus, and t)Ccasionally on other algie. l''or 

 the study of larval development, colonies of one or two 

 scasotts' growth taken close to low water-mark proved 

 the most suitable. .Such colonies contain abundance of 

 spermatozoa, or of ova or larvte, according to the 

 season, the reproductive period being from i""ebruary 

 to August. In pure running water t'luiirclla hispida 

 may be usually kept alive in tanks for a few days to a 

 week. The larva; were examined in the living state 

 and after fixation; the fixatives used were: (i) Satu- 

 rated sublimate with 5 per cent, acetic acid; (2) 5 per 

 cent, chromic acid, 100 parts, with 5 drops acetic acid; 

 (3) Flemming; (4) Hermann; (5) Chromo-nitro-osmic 

 mixture; (6) .Vcetic alcohol, with sublimate to satura- 

 tion; (7) Kleinenbcrg. .After fixation, the material was 

 removed to 70 per cent, alcohol. Chrom-acetic acid 

 and corrosive acetic gave the best results for fixation 

 in bulk. Larvas were isolated by slicing off the front 

 wall of the colony with a razor; the larvEe lie just below 

 tills wall, enclosed in the tentacle-sheath. For isolated 

 larvte, the best fixatives were corrosive acetic and 

 acetic alcohol, saturated with sublimate. Kntire eggs 

 and larvEe were examined during life and after fixation. 

 The latter were stained with borax-carmine or with 

 saffranin. In some ca.scs the nuclear spindles and the 

 yolk-nucleus were clearly brought out. Sections were 

 made from isolated lar\-{e, and of colonics containing 

 larva-. Groups of isolated larvae w^ere embedded to- 

 gether, and sections obtained in various planes. In 

 order to determine the direction of unorientated larva", 

 a set of standard .sections was prepared by carefully 

 orientating single larvaB, which had been first studied 

 entire. To ensure thorough impregnation of colonies 

 with larva; in siiii, the material was left in xylol for 

 about a week before being passed through xylol-paraffin 

 to paraffin. The most useful stain for sections was 

 Heidenhain's iron-ha-matoxylin, followed by eosin in 

 90 per cent, alcohol. Other stains were u.sed, among 

 which was Mayer's muci-carmine, for detecting the 

 presence of mucin. 



Differentiation of Typhoid Bacillus. 



The " British Medical Journal " gives a summary of 

 a method advocated by Lcefl!ler for differentiating 

 typhoid bacilli from nearly allied organisms, by the 

 u.se of media to which malachite green has been added. 

 One of these media contains 2 per cent, peptone and 

 I per cent, nutro.se in loo c. cm. of distilled water, and 

 is neutralised bv the addition of t.o6 c. cm. of normal 

 potash. To this is added 5 per cent, of milk sui,Mr 

 and I p;r cent, of grape sugar. ,\fter boiling for a 



