Clinical tuberculosis . lass beads which cast shadows of 2, 4, and 6microns upon the microscopic field, using Bausch and Lombeyepiece 1 inch or lOx, objective /42th, focal distance 160 mm.(see Fig. 100). These glass beads are made by drawing outvery fine glass filaments in the flame. They are then fused onthe end in a very small flame, preferably fioiii an alcohol are then standardized with the stage and eye-piece micro- 566 LABORATORY METHODS meters, and those selected which arc of the desired the manufacturers do not make their oil immer-sioia lenses exactl
Clinical tuberculosis . lass beads which cast shadows of 2, 4, and 6microns upon the microscopic field, using Bausch and Lombeyepiece 1 inch or lOx, objective /42th, focal distance 160 mm.(see Fig. 100). These glass beads are made by drawing outvery fine glass filaments in the flame. They are then fused onthe end in a very small flame, preferably fioiii an alcohol are then standardized with the stage and eye-piece micro- 566 LABORATORY METHODS meters, and those selected which arc of the desired the manufacturers do not make their oil immer-sioia lenses exactly of the same magnification, so that one can-not use the device in different microscopes unless the ocular andobjective systems are exactly the same. I have three B & Lyi2 oil immei-sion lenses, and the relative magnifying powers , 75, and This results in a variation of about 10 pointsin index in comparisons which I have made, between the firstand last objectives. There would be a great advantage if the. Fig. 100.—Device for classifying tubercle bacilli according to length. A, B, and C,fine glass filaments supporting glass beads which cast shadows of 2, 4 and 6 micronsrespectively, upon the microscopic field. method could be carefully standarized so that a given indexwould mean the same regardless of the instrument used. Because of the ease with which the device may be broken,I have attempted to find some substitute. A special disc wasmade by the manufacturer upon which were made three circularetchings of the proper size; but it was necessary to discard thedevice because the etchings did not show up plainly. With alittle patience I believe that anyone familiar with micrometry LENGTH INDEX OF BACILLI 567 can manufacture the device for himself. I have used mine forfifteen months- without breaking. Using a mechanical stage all bacilli that pass between beads2 n. and 6 /x. are classified. This can be done quite rapidly, andin most preparations it is not necessary to
Size: 1578px × 1582px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookpublisherstlou, bookyear1922
