. The physiology of the Invertebrata. forms of this important instrument of re-? search. The one used by Mr. E. B. Poulton, , in his investi-gations on the blood of the Lepidoptera is illustrated inFig. 32. This instrument has the slit mechanism betweenthe lenses. The upper achromatic lens is adjustable to theslit; an Amici prism is placed over the eyepiece, and thewhole connected with the body by a clamping screw. Themechanism worked by the screw P is for contracting andexpanding the slit by the symmetrical movement of both PHYSIOLOGY OF THE INVERTEBRATA. 171 edges. This opens so widely
. The physiology of the Invertebrata. forms of this important instrument of re-? search. The one used by Mr. E. B. Poulton, , in his investi-gations on the blood of the Lepidoptera is illustrated inFig. 32. This instrument has the slit mechanism betweenthe lenses. The upper achromatic lens is adjustable to theslit; an Amici prism is placed over the eyepiece, and thewhole connected with the body by a clamping screw. Themechanism worked by the screw P is for contracting andexpanding the slit by the symmetrical movement of both PHYSIOLOGY OF THE INVERTEBRATA. 171 edges. This opens so widely as to permit a view of thewhole visual field. The slit is shortened by the screw H, sothat when the comparison prism is inserted the aperture iscontracted to such an extent that the image of the objectunder investigation completely fills it, .There is a comparisonprism, with lateral frame and clips to hold the comparedobject and the mirror; all these parts are fixed in a drumcombined with the eyepiece. Above the eyepiece there is. Fig. 32.—The Abbe-Zeiss Mickospecteoscope. I = Microspectroscope (half actual size). 2 = Drum with mechanismof the slit (actual size). an Amici prism of great dispersion, which turns aside on apivot, leaving the eyepiece unobstructed for adjustment toan object K; the axial position of the prism is indicatedby the spring L, which keeps it in place. A scale is projectedon the spectrum by means of a small scale-tube and mirrorattached to the mount of the prism. The divisions of thescale give the wave-lengths of that section of the spectrumon which they fall in fractions of a micromillimetre, wherebythe second deqimal place may be read oflF directly, and the 172 PHYSIOLOGY OF THE INVERTEBRATA. third calculated by estimation. The position of the scalerelative to the spectrum is adjusted by a screw P on thejacket of the Amici prism. Pig. 33 represents Dr. Engelmanns microspectrometer,which is constructed on the principle of Vierordts spectro-photometer f
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectinverte, bookyear1892
